Question

1. One stats class consists of 52 women and 28 men.  Assume the average exam score on Exam 1 was 74 (σ = 10.43; assume the whole class is a population).

   A random sample of 16 students yielded an average of a 75 on the first exam (s=16). What is the z-score of the sample mean? Is this sample significantly different from the population? (Hint: Use the z-score formula for locating a sample mean)

   		-0.67, sample is not significantly different from the population.
   		0.38, sample is not significantly different from the population.
   		-0.67, sample is significantly different from the population.
   		0.38, sample is significantly different from the population.

QUESTION 8

1. One stats class consists of 52 women and 28 men.  Assume the average exam score on Exam 1 was 74 (σ = 10.43; assume the whole class is a population).

   Assume you wanted to find out which two exam scores encompassed the 75% middle of the class.  Which two exam scores would that be? (HINT: use algebra to re-arrange the z-score equation).

   		65.04
   		62.01
   		75.34
   		85.99

Answer 1

1)

Sample mean =m=75

Population mean ==74

n=16

Now Z score for sample mean

Since Z score is very less so it will not give sugnificant result.

Hence correct answer is

0.38, sample is not significantly different from the population

Question 8)

We have to find values within which middle 75% lies

First we find the limits in Z score form then we will convert it in score form now

Let 75% values lies within -z and z

So

P(-z<Z<z)=0.75

=P(Z<z)-P(Z<-z)

=P(Z< z)-(1-P(Z<z))=0.75

=2P(Z< z )=1.75

This gives

P(Z< z )=0.875

Also from.Z table

P(Z<1.15)=0.875

Hence z=1.15

So interval is (-1.15,1.15)

Now let a and b are two limits in score form then

Hence options 62.01 and 85.99 are correct