Question

3.5 Each year NPR has a fundraising week. Last year the mean contribution per individual was $120. They want to see if the mean contribution per individual has gone down this year. A random sample of 30 contributors was taken and the sample mean was $110 with a sample standard deviation of $25. Using a = .01, test the station's claim that the mean contribution has gone down. 344. How can you reduce the width of a confidence interval without lowering your confidence level?

Answer 1

e Hilch 120 to 120 than Define the nell hypothesis and alternative hazpothesis. Ho ll= 120 vs Hill cho 120 are value of test static is t= 25/ So, value of test static is - 2.19 As test is left tailed and number of If freedom 30-1=29, So, p-value is I Plte-2.19)=0.0184 AS 0.0184 70.of so we fail to repect null Mypothesis. we lenge of the interval is inversate tuess inversely boobostional to the sample size.. So to reduce the width of the Confidente interval increase the sample pe.