Question

find the following critical t-scores

Near the beginning of the semester, you administered a survey to 10 students. Suppose we wanted to use your sample to calculate the mean age of college students. What are the critical t-scores for the mean age using your sample?

80% CI: t =

90% CI: t =

99% CI: t =

Answer 1

solution:

a.

Degrees of freedom = df = n - 1 =10 - 1 = 9

At 80% confidence level the t is ,

= 1 - 80% = 1 - 0.80 = 0.2

/ 2 = 0.2 / 2 = 0.1

t /2  df = t0.1,9= 1.383    ( using student t table)

b.

Degrees of freedom = df = n - 1 =10 - 1 = 9

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

/ 2 = 0.1 / 2 = 0.05

t /2,df = t0.05,9 =1.833    ( using student t table)

c.

Degrees of freedom = df = n - 1 =10 - 1 = 9

At 99% confidence level the t is ,

= 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

t /2  df = t0.005,9 = 3.250 ( using student t table)