a)Calculate the variance of the random variable X which is the mean of the weights of the 77 AMs from 2019.  b)Calculate the variance of the random variable Y, which is the mean of the weights of the 93 AMs from 1999.  c) Calculate the variance of X - Y?

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It has long been assumed that first year college students gain weight during their first semester. During the last year, some college students have lived on campus (OC) and some have gone to school remotely (RM). Do on campus students gain more weight than remote students? A random sample 77 OC students had a mean weight gain of x = 3.46 pounds. A random sample 93 RMs a mean weight of y = 2.35 pounds. It is recognized that the true standard deviation of OC weight gain is 

?x

 = 3.16 pounds while it is recognized that the true standard deviation of RM weight gain is 

?y

 = 2.07 pounds. The true (unknown) mean OC weight gain is 

?x

 pounds, while the true (unknown) mean of RM weight gain is 

?y

 pounds. Weights are known to be a normally distributed. In summary:

Type Sample Size Sample Mean Standard Deviation
On campus data(OC) 77 3.46 3.16
Remote data (RM)) 93 2.35 2.07



a)Calculate the variance of the random variable X which is the mean of the weights of the 77 AMs from 2019. 

b)Calculate the variance of the random variable Y, which is the mean of the weights of the 93 AMs from 1999. 

c) Calculate the variance of X - Y? 

d) Calculate the standard deviation of X - Y? 
.
e) If we wish to create an 98% confidence interval for 

?x

 - 

?y

 then what is the z critical value used? 

f)Create an 98% confidence interval for 

?x

 - 

?y

. (

 , 

)

g) What is the length of your 98% confidence interval for 

?x

 - 

?y



h) If we used this data to test 

H0:
?x

 - 

?y

=0 against the alternative 

Ha:
?x

 - 

?y

 > 0 then what would the value of the calculated test statistic z have been? 

i) If we used this data to test 

H0:
?x

 - 

?y

=0 against the alternative 

Ha:
?x

 - 

?y

>0 then what would the p value have been? 

j)If we used this data to test 

H0:
?x

 - 

?y

=0 against the alternative 

Ha:
?x

 - 

?y

≠0 then what would the p value have been?

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