Based on her weight and pace, Kate burns 586 calories when she runs 5 miles. How many calories will she burn if she runs only 3 miles? How many miles (to the nearest mile) does she need to run each week if she wants to burn one pound (3500 calories) of body fat each week?
Answers
Answer:
Dear dandrexbox
Answer to your query is provided below
She will burn 351.6 calories if she run 3 miles.
She needs to run 4 miles (approx) per day for a week to burn one pound calories.
Step-by-step explanation:
Explanation for the same is attached in image
Related Questions
A, B, and C are collinear points. B is between A and C. AB = 5x + 8 BC = 6x - 1 AC = 12x - 11 Find AC.
Answers
Answer:
AC = 198
Step-by-step explanation:
Since all these points are collinear, we know that the addition of AB plus BC should give the same as AC. We can then set an equation that addresses this identity:
AB + BC = AC
5x +8 +6x - 1 = 12x - 11
Now re-arranging like terms in order to combine them:
8 - 1 + 11 = 12x - 5x - 6x
19 - 1 = 12x - 11x
18 = x
Now that we know the value of 'x", we can determine the value of AC:
AC = 12x - 11
AC = 12 (18) - 11
AC = 216 - 18
AC = 198
Merely needs to add enough water to 11 gallons of an 18% detergent solution to make 12% detergent solution which equation can she used to find g the number of gallon of water she should add?
Answers
1 × 18/100 = 12/100(g+11), is the equation. The answer is 12/100 gallons
Find the diameter and radius of a circle with a circumference of 65.98 Please help
Answers
Answer:
21 and 10.5 respectively
Step-by-step explanation:
Remember circumference of a circle is given as;
C= 2×π×r; r is raduis
r = C / 2×π
=65.98/(2×3.142)= 10.50
D= 2× r = 2× 10.50= 21.0( D represent diameter)
Note π = 3.142 a known constant
The mean percent of childhood asthma prevalence in 43 cities is 2.32%. A random sample of 32 of these cities is selected. What is the probability that the mean childhood asthma prevalence for the sample is greater than 2.8%? Interpret this probability. Assume that sigmaequals1.24%. The probability is nothing.
Answers
Answer:
[tex] P(\bar X>2.8)[/tex]
We can use the z score formula given by:
[tex] z=\frac{\bar X -\mu}{\frac{\sigma}{\sqrt{n}}}[/tex]
And replacing we got:
[tex] z=\frac{2.8 -2.32}{\frac{1.24}{\sqrt{32}}}=2.190 [/tex]
And using the normal standard distribution and the complement rule we got:
[tex] P(z>2.190 )= 1-P(z<2.190) = 1-0.986=0.014[/tex]
Step-by-step explanation:
For this case w eknow the following parameters:
[tex] \mu = 2.32[/tex] represent the mean
[tex]\sigma =1.24[/tex] represent the deviation
n= 32 represent the sample sze selected
We want to find the following probability:
[tex] P(\bar X>2.8)[/tex]
We can use the z score formula given by:
[tex] z=\frac{\bar X -\mu}{\frac{\sigma}{\sqrt{n}}}[/tex]
And replacing we got:
[tex] z=\frac{2.8 -2.32}{\frac{1.24}{\sqrt{32}}}=2.190 [/tex]
And using the normal standard distribution and the complement rule we got:
[tex] P(z>2.190 )= 1-P(z<2.190) = 1-0.986=0.014[/tex]
Answer:
0.55% probability that the mean childhood asthma prevalence for the sample is greater than 2.8%. This means that a sample having an asthma prevalence of greater than 2.8% is unusual event, that is, unlikely.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal probability distribution
When the distribution is normal, we use the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
If X is more than two standard deviations from the mean, it is considered an unusual outcome.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
In this question, we have that:
[tex]\mu = 2.32, \sigma = 1.24, n = 43, s = \frac{1.24}{\sqrt{43}} = 0.189[/tex]
What is the probability that the mean childhood asthma prevalence for the sample is greater than 2.8%?
This is 1 subtracted by the pvalue of Z when X = 2.8. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
By the Central Limit Theorem
[tex]Z = \frac{X - \mu}{s}[/tex]
[tex]Z = \frac{2.8 - 2.32}{0.189}[/tex]
[tex]Z = 2.54[/tex]
[tex]Z = 2.54[/tex] has a pvalue of 0.9945
1 - 0.9945 = 0.0055
0.55% probability that the mean childhood asthma prevalence for the sample is greater than 2.8%. This means that a sample having an asthma prevalence of greater than 2.8% is unusual event, that is, unlikely.
PLEASE HELP ME GUYS!!
Answers
Answer:
[tex]\frac{7}{3}[/tex]
Step-by-step explanation:
csc(Ф) is equivalent to the inverse of sin(Ф)
[tex]csc = \frac{1}{sin}[/tex]Since sin(Ф) = 3/7, the inverse of this would be 7/3
So, [tex]csc = \frac{1}{\frac{3}{7} }=\frac{7}{3}[/tex]
1. You have a home business selling designer necklaces. You have done
some market research, which shows that at a price of $40 you can sell
500 per week, and at a price of $60 you can sell 400 per week. Assuming
that the relationship between price and quantity sold is linear, find the
price that maximizes revenue. You must use methods that we developed
and practiced in the course. You will be graded not only on your answer
but on the clarity of your presentation.
Answers
Answer:
The price that maximizes the profits from the sale of the product is $60.
Step-by-step explanation:
Since selling necklaces at $ 40 allows a total amount of 500 sales per week, while a price of $ 60 allows 400 sales at the same time, the following calculations must be made to determine the price that maximizes sales performance:
40 x 500 = $ 20,000
60 x 400 = $ 24,000
50 x 450 = $ 22,500
55 x 425 = $ 23,375
58 x 410 = $ 23,780
59 x 405 = $ 23,895
As can be seen from the calculations developed, the price that maximizes the profits from the sale of the product is $60.
Jack has a rectangular patio with a length that is one foot less than twice its width. His neighbor Ron's patio has the same width but a length that is 5 feet more than its width. If Jack's patio is 120 square feet and Ron's patio is 104 square feet, how many square feet longer is Jack's patio than Ron's?
Answers
Answer:
difference in area = 16 ft²
if you use 8 the difference in length between Jack patio and his neighbor patio will be will be 15 - 13 = 2 ft
if you use 13 the difference i length will be 25 - 18 = 7 ft
Step-by-step explanation:
Jacks rectangular patio
width = a
length = 2a - 1
area = lw
where
l = length
w = width
area = 120 ft²
a(2a - 1)
2a² - a - 120 = 0
(a - 8) (2a + 15)
a = 8 or -15/2
Ron's rectangular patio
width = a
length = a + 5
area = lw
area = 104 ft²
a (a + 5) = 104
a² + 5a -104 = 0
(a + 8) (a - 13)
a = -8 or 13
How many square feet longer is jack patio longer than Ron's patio is the difference in their area. Therefore,
120 - 104 = 16 ft²
The value 8 or 13 can be used for a since the width a have to be the same.
if you use 8 the difference in length between Jack patio and his neighbor patio will be will be 15 - 13 = 2 ft
if you use 13 the difference i length will be 25 - 18 = 7 ft
What is the final step in solving the inequality –2(5 – 4x) < 6x – 4?
Answers
Answer:
–2(5 – 4x) < 6x – 4
<=>
-10 + 8x < 6x - 4
<=>
2x < 6
<=>
x < 3
Hope this helps!
:)
Answer:
Step 1: –10 + 8x < 6x – 4
Step 2: –10 < –2x – 4
Step 3: –6 < –2x
Step 4: ________
What is the final step in solving the inequality –2(5 – 4x) < 6x – 4?
A. x < –3
B. x > –3
C. x < 3
D. x > 3
Step-by-step explanation:
The correct answer here is C. x < 3
Find x in this 45°-45°-90° triangle.
145972
x
X=
4.572
9
18
Answers
A rectangle has an area of 96cm2 it's length is 4cm longer than it's width. Calculate the length and width.
Answers
Answer:
I think l
Step-by-step explanation:
first add 96 and4 then 2 I think
select the point that is a solution to the system of inequalities
Answers
This point is below both the red diagonal line and the blue parabola. We know that the set of solution points is below both due to the "less than" parts of each inequality sign.
In contrast, a point like (2,2) is above the parabola which is why it is not a solution. It does not make the inequality [tex]y \le x^2-3x[/tex] true. So this is why we can rule choice A out.
Choice C is not a solution because (4,1) does not make [tex]y \le -x+3[/tex] true. This point is not below the red diagonal line. We can cross choice C off the list.
Choice D is similar to choice A, which is why we can rule it out as well.
The president of a university claimed that the entering class this year appeared to be larger than the entering class from previous years but their mean SAT score is lower than previous years. He took a sample of 20 of this year's entering students and found that their mean SAT score is 1,501 with a standard deviation of 53. The university's record indicates that the mean SAT score for entering students from previous years is 1,520. He wants to find out if his claim is supported by the evidence at a 5% level of significance. True or False: The null hypothesis would be rejected.
Answers
Answer:
False.
The null hypothesis failed to be rejected.
At a significance level of 5%, there is not enough evidence to support the claim that the entering class has a mean SAT score that is significantly lower than 1520.
Step-by-step explanation:
This is a hypothesis test for the population mean.
The claim is that the entering class has a mean SAT score that is significantly lower than 1520.
Then, the null and alternative hypothesis are:
[tex]H_0: \mu=1520\\\\H_a:\mu< 1520[/tex]
The significance level is 0.05.
The sample has a size n=20.
The sample mean is M=1501.
As the standard deviation of the population is not known, we estimate it with the sample standard deviation, that has a value of s=53.
The estimated standard error of the mean is computed using the formula:
[tex]s_M=\dfrac{s}{\sqrt{n}}=\dfrac{53}{\sqrt{20}}=11.851[/tex]
Then, we can calculate the t-statistic as:
[tex]t=\dfrac{M-\mu}{s/\sqrt{n}}=\dfrac{1501-1520}{11.851}=\dfrac{-19}{11.851}=-1.6[/tex]
The degrees of freedom for this sample size are:
[tex]df=n-1=20-1=19[/tex]
This test is a left-tailed test, with 19 degrees of freedom and t=-1.6, so the P-value for this test is calculated as (using a t-table):
[tex]\text{P-value}=P(t<-1.6)=0.063[/tex]
As the P-value (0.063) is bigger than the significance level (0.05), the effect is not significant.
The null hypothesis failed to be rejected.
There is not enough evidence to support the claim that the entering class has a mean SAT score that is significantly lower than 1520.
A spinner is divided into 8 equal sections, and each section contains a number from 1 to 8. What is the probability of the spinner landing on 5? A. 1 over 13 B.1 over 8 C.5 over 13 D.5 over 8 PLEASE HURRY!!!!!!!!!!!!!!!!!
Answers
Answer:
B. 1 over 8
Step-by-step explanation:
To determine the probability of the spinner landing on 5, we need to first know what probability is,
probability = required outcome/all possible outcome
since the spinner is divided into 8 equal sections and each section contains number from 1-8, this implies there are total of 64 numbers on the spinner. This implies that all possible outcome = 64
In each section there is 5, since there are 8 sections on the spinner, the number of 5's on the spinner are 8.
This implies that the required outcome = 8
but
probability = required outcome/all possible outcome
probability (of the spinner landing on 5) = 8/64 =1/8
Answer:
b
Step-by-step explanation:
Which of the following is most likely the next step in the series?
Answers
Answer:
B
Step-by-step explanation:
They are increasing by 1 vertically. Hope this helps!! :)
What is the solution of the following linear system? y = 3x + 1 2y = 6x + 2
Answers
Answer:
y = 3x +1 (1)
2y = 6x +2 (2)
We can devide equation (2) by 2 and we got:
[tex] y =3x +1[/tex] (3)
And since equations (1) and (3) are equal we can do this:
[tex] 3x +1 = 3x+1[/tex]
And that implies:
[tex] 0=0[/tex]
And for this case we will have infinite solutions for the sytem given since we have two lines equal
Step-by-step explanation:
For this case we have the following system of equations given:
y = 3x +1 (1)
2y = 6x +2 (2)
We can devide equation (2) by 2 and we got:
[tex] y =3x +1[/tex] (3)
And since equations (1) and (3) are equal we can do this:
[tex] 3x +1 = 3x+1[/tex]
And that implies:
[tex] 0=0[/tex]
And for this case we will have infinite solutions for the sytem given since we have two lines equal
1. Mrs. Verner's class has
a total of 15 students. If 8
of them are girls, what
percentage are boys?
Answers
Answer:
46.7%
Step-by-step explanation:
Given:
Total number of students in Mrs. Verner's class = 15
Number of girls = 8
To find: percentage are boys
Solution:
Percentage of boys = ( Number of boys / Total number of students ) × 100
Number of boys = Total number of students - Number of girls = 15 - 8 = 7
So,
Percentage of boys = [tex]\frac{7}{15}[/tex] × 100 = 46.7%
The mean of three numbers is 4
Two of the numbers are 1, 9
What is the missing number?
Answers
Answer:2
Step-by-step explanation: 9+1+2=12
12\3=4
ANSWER : 2
(9+1+x)/3=4
(10+x)/3=4
10+x= 3*4
x= 12 -10
x= 2
Determine 6m 9m how much greater the area of the yellow rectangle is than the area of the gree rectangle 2m 5m
Answers
Step-by-step explanation:
multiple 6 by 9 then 2 by 5 then subtract them
Answer:
44
Step-by-step explanation:
(6*9) - (2*5)
54 - 10
44
A bag contains 1p,20 and 5p coins 3/8 of the bag are 1p coins There are as many 5p coins as 1p coins in the bag. There are 640 coins in total. Work out the number of 20 coins in the bag
Answers
Answer:
160 off 20p coins
Step-by-step explanation:
1 p, 20 p, 5 p coins1 p= 3/8 of the bag5 p= 1 p= 3/8 of the bagtotal coins= 64020 p coins= 640 - 640*(3/8+3/8)= 640*(1- 6/8)= 640 * 2/8= 640* 1/4= 160
20p coins = 640 -640*(3/8+3/8)=640*(-16/8)=640 *2/8=640*1/4=160
Jaleel and Lisa are simplifying the expression 2(x-2) + 2 as shown
Answers
Answer:
Jaleel is correct because 2 (x + 2) = 2x - 4
Step-by-step explanation:
To solve 2 (x - 2) + 2:
2 (x - 2) + 2
Distribute
2x - 4 + 2
Combine like terms
2x - 2
Lisa did not distribute correctly :)
Answer:
D
Step-by-step explanation:
Can someone please help me with this question the first one
Answers
The pressure p(in lbs/in^2) that a 160 pound persons shoe exerts on the ground when walking varies inversely with the area A(in in^2) of the sole of the shoe when the shoes have a sole area of 40 in^2 The pressure is 4 lbs/in^2 find equation that relates these variables
A=
Answers
Answer:
[tex]A = \dfrac{40}{P}[/tex]
Step-by-step explanation:
Pressure [tex]p(in lbs/in^2)[/tex] varies inversely with the area [tex]A(in$ in^2)[/tex] of the sole of the shoe.
This is written as:
[tex]P \propto \frac{1}{A}\\ $Introducing the constant of variation$\\P = \dfrac{k}{A}[/tex]
When:
[tex]When: A= 40 in^2, P =4 lbs/in^2\\$Substituting into the equation\\P = \dfrac{k}{A}\\4 = \dfrac{k}{40}\\$Cross multiply\\k=4*40\\k=160\\Therefore, the equation that connect these variables is given as:\\P = \dfrac{40}{A}\\$In terms of P\\AP=40\\\\A = \dfrac{40}{P}[/tex]
Ronnie invested $1500 in an account that earns 3.5% interest, compounded annually. The formula for compound interest is A(t) = P{(1 + i)^t}A(t)=P(1+i) t . How much did Ronnie have in the account after 4 years?
Answers
Answer:
BStep-by-step explanation:
A= New amount
P= Principal or Original amount which is £1500
I= Interest
t= time period
3.5% as a decimal is 3.5÷100=0.035
time period= 4 years
so 1500(1+0.035)^4 = B
Omar has three t shirts: one red, one green and one yellow. He has two pairs of shorts one black and red.
-How many different outfits can Omar put together?
-What is the probability of Omar’s outfits including a red T-shirt or red shorts?
Answers
Answer:
Omar can put together 6 outfits.
66.67% probability of Omar’s outfits including a red T-shirt or red shorts
Step-by-step explanation:
A probability is the number of desired outcomes divided by the number of total outcomes.
-How many different outfits can Omar put together?
For each t-shirt, that are two options of shorts.
There are 3 t-shirts.
3*2 = 6
Omar can put together 6 outfits.
What is the probability of Omar’s outfits including a red T-shirt or red shorts?
Red t-shirt and red shorts
Red t-shirt and black shorts
Green shirt and red shorts
Yellow shirt and red shorts
4 desired outcomes.
4/6 = 0.6667
66.67% probability of Omar’s outfits including a red T-shirt or red shorts
The lifespan (in days) of the common housefly is best modeled using a normal curve having mean 22 days and standard deviation 5. Suppose a sample of 25 common houseflies are selected at random. Would it be unusual for this sample mean to be less than 19 days?
Answers
Answer:
Yes, it would be unusual.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal probability distribution
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
If [tex]Z \leq -2[/tex] or [tex]Z \geq 2[/tex], the outcome X is considered unusual.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
In this question, we have that:
[tex]\mu = 22, \sigma = 5, n = 25, s = \frac{5}{\sqrt{25}} = 1[/tex]
Would it be unusual for this sample mean to be less than 19 days?
We have to find Z when X = 19. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
By the Central Limit Theorem
[tex]Z = \frac{19 - 22}{1}[/tex]
[tex]Z = -3[/tex]
[tex]Z = -3 \leq -2[/tex], so yes, the sample mean being less than 19 days would be considered an unusual outcome.
Devon wants to build a ramp with the dimensions shown. How much wood does he need?
Answers
The image of the ramp with dimensions is missing, so i have attached it.
Answer:
680 in² of wood is needed.
Step-by-step explanation:
The way to find how much wood would be needed by devon would be to find the total surface area of the ramp.
From the attached image,
Let's find the area of the 2 triangles first;
A1 = 2(½bh) = bh = 15 x 8 = 120 in²
Area of the slant rectangular portion;
A2 = 17 x 14 = 238 in²
Area of the base;
A3 = 15 × 14 = 210 in²
Area of vertical rectangle;
A4 = 8 × 14 = 112 in²
Total Surface Area = A1 + A2 + A3 + A4 = 120 + 238 + 210 + 112 = 680 in²
Among 25- to 30-year-olds, 29% say they have used a computer while under the influence of alcohol. Suppose five 25- to 30-year-olds are selected at random. Complete parts (a) through (d) below. (a) What is the probability that all five have used a computer while under the influence of alcohol? (Round to four decimal places as needed.) (b) What is the probability that at least one has not used a computer while under the influence of alcohol? (Round to four decimal places as needed.) (c) What is the probability that none of the five have used a computer while under the influence of alcohol? (Round to four decimal places as needed.) (d) What is the probability that at least one has used a computer while under the influence of alcohol? (Round to four decimal places as needed.)
Answers
Answer:
(a) The probability that all five have used a computer while under the influence of alcohol is 0.0021.
(b) The probability that at least one has not used a computer while under the influence of alcohol is 0.9979.
(c) The probability that none of the five have used a computer while under the influence of alcohol is 0.1804.
(d) The probability that at least one has used a computer while under the influence of alcohol is 0.8196.
Step-by-step explanation:
We are given that among 25- to 30-year-olds, 29% say they have used a computer while under the influence of alcohol.
Suppose five 25- to 30-year-olds are selected at random.
The above situation can be represented through the binomial distribution;
[tex]P(X = x) = \binom{n}{r}\times p^{r} \times (1-p)^{n-r} ; x = 0,1,2,3,.........[/tex]
where, n = number of trials (samples) taken = Five 25- to 30-year-olds
r = number of success
p = probability of success which in our question is probability that
people used a computer while under the influence of alcohol,
i.e. p = 29%.
Let X = Number of people who used computer while under the influence of alcohol.
So, X ~ Binom(n = 5, p = 0.29)
(a) The probability that all five have used a computer while under the influence of alcohol is given by = P(X = 5)
P(X = 5) = [tex]\binom{5}{5}\times 0.29^{5} \times (1-0.29)^{5-5}[/tex]
= [tex]1 \times 0.29^{5} \times 0.71^{0}[/tex]
= 0.0021
(b) The probability that at least one has not used a computer while under the influence of alcohol is given by = P(X [tex]\geq[/tex] 1)
Here, the probability of success (p) will change because now the success for us is that people have not used a computer while under the influence of alcohol = 1 - 0.29 = 0.71
SO, now X ~ Binom(n = 5, p = 0.71)
P(X [tex]\geq[/tex] 1) = 1 - P(X = 0)
= [tex]1-\binom{5}{0}\times 0.71^{0} \times (1-0.71)^{5-0}[/tex]
= [tex]1 -(1 \times 1 \times 0.29^{5})[/tex]
= 1 - 0.0021 = 0.9979.
(c) The probability that none of the five have used a computer while under the influence of alcohol is given by = P(X = 0)
P(X = 0) = [tex]\binom{5}{0}\times 0.29^{0} \times (1-0.29)^{5-0}[/tex]
= [tex]1 \times 1 \times 0.71^{5}[/tex]
= 0.1804
(d) The probability that at least one has used a computer while under the influence of alcohol is given by = P(X [tex]\geq[/tex] 1)
P(X [tex]\geq[/tex] 1) = 1 - P(X = 0)
= [tex]1-\binom{5}{0}\times 0.29^{0} \times (1-0.29)^{5-0}[/tex]
= [tex]1 -(1 \times 1 \times 0.71^{5})[/tex]
= 1 - 0.1804 = 0.8196
Any help would be great
Answers
Answer:
88/57
Step-by-step explanation:
Answer: 88:57
Step-by-step explanation:
Length is 88 and width is 57
So the ratio is 88:57
The sum of two fractions can always be written as a
Answers
Answer: decimal
Step-by-step explanation:
because i did this quiz
Determine whether the description corresponds to an observational study or an experiment.
Research is conducted to determine if there is a relation between hearing loss and exposure to mumps. exposure to mumps.
Does the description correspond to an observational study or an experiment?
A. Observational study
B. Experiment
Answers
Answer:
A. Observational study
Step-by-step explanation:
In research, an observational study is a type of study in which the researcher observes a phenomenon and tries to establish some relationship between the different variables he/she is observing. In other words, the researcher only observes and doesn't give a treatment.
On the other hand, when we have a experiment, we usually have 2 different groups (one that will receive a treatment and one who won't) and the researcher compares the differences between these two groups because of the treatment. In other words, the researcher does something other than just observing.
In this example, the research is going to determine if there is a relation between hearing loss and exposure to mumps. In this example the researcher is only going to observe how people who have been exposed to mumps are regarding hearing loss (we can say this since it will be unethical for example for the researcher to create an experiment in which he/she exposes a group to mumps). Therefore, he is going to observe how the past exposure to mumps could be related with the hearing loss.
Thus, this is an observational study.