Use table c to find the critical value t that you would use

Use table c to find the critical value t* that you would use for confidence intervals for the mean of the population in each ofthe following situations.

Question
    A 99% confidence interval based on n=10 observations?
    A 98% confidence interval from an SRS of 20 observations?
    A 80% confidence interval from a sample of size 7?

The composition of the earth

Solution

a) t critical for 99% df = 9 is 1.8331

b) 98% conf int for df =19 is 2.5395

c) 80% conf int for df 6 = 3.1426

First for the sample given find mean and std dev

Mean = 59.59

std dev = 5.90

80% confidence interval :

Margin of error =