Question

Your instructor (Katie) believes that the average time of taking this exam is equal to 140 minutes. A sample of 4 students was taken and the following exam times were obtained. Assume the distribution of the population is normally distributed. Sample: 150, 150, 180, 170 (Sample Std. Dev = 15) The value of test statistic is: O a.-1.5 O b.1.5 OC -3 O d. 3

Answer 1

Given :

$\mu = 140$

$n=4$

Sample : 150 , 150 , 180 , 170

As the population standard deviation is unknown ( not given ) , we need to use t-test statistic .

The formula for test statistic is ,

$t = \frac{\bar{x}-\mu }{\frac{s}{\sqrt{n}}}$

$\bar{x} = \frac{\sum{x}}{n}=\frac{150+150+180+170}{4}$

$\bar{x} =162.5$

$t = \frac{\bar{x}-\mu }{\frac{s}{\sqrt{n}}}$

$t = \frac{162.5-140}{\frac{15}{\sqrt{4}}}$

The value of test statistic is : 3