5. One of the few negative side effects of quitting smoking is weight gain. To e

Question

5. One of the few negative side effects of quitting smoking is weight gain. To estimate the mean weight gain, a random sample of 25 quitters was drawn and it was found that the mean is 25 pound and the standard deviation is 6 pounds. Determine a 95% confidence interval of the mean for all quitters. 6. A sample of 40 sales receipts from a grocery store has $137 and standard deviation $30.2. Use these values to test whether or not the mean of sales at the grocery store is less than $150 a). Set the null and alternative hypotheses. b). Calculate the test statistic. c). Find the T-critical value from the Table (with a 0.05). d). Make your conclusion at a 0.05.

Explanation / Answer

5)std errrof mean =std deviation/(n)1/2 =1.2

at 24 degree of freedom and 95% CI, t=2.0639

95% confidence interval =sample mean -/+ t*Std error =22.52 ; 27.48

6)null hypothesis: mean =150

alternate hypothesis: mean<150

std errrof mean =std deviation/(n)1/2 =4.775

hence test stat t=(X-mean)/std error=(137-150)/4.775 =-2.7225

critical value =-1.685

as test stat is below critical value we reject null hypothesis and conclude that mean is less then 150

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