2 Degrees of Freedom For the accompanying screen display a s

2. Degrees of Freedom For the accompanying screen display, a simple random sample of size n = 40 was obtained from the population of duration times (seconds) of eruptions of the Old Faithful geyser. a. What is the number of degrees of freedom that should be used for finding the critical value t alpha/2? b. Find the critical value t alpha/2 corresponding to n = 40 and a 95% confidence level. c. Give a brief general description of the number of degrees of freedom. 3. Interpreting a Confidence Interval The results in the screen display are based on a 90% confidence level. Write a statement that correctly interprets the confidence interval.

Solution

(a) The degree of freedom =n-1=40-1=39

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(b) Given a=0.05, the critical value is t(0.025, df=39) =2.02 (from student t table)

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(c) The number of degree of freedom is n-1=39