Question

The average daily volume of a computer stock in 2011 was mu equals35.1 million​ shares, according to a reliable source. A stock analyst believes that the stock volume in 2014 is different from the 2011 level. Based on a random sample of 40 trading days in​ 2014, he finds the sample mean to be 28.9 million​ shares, with a standard deviation of sequals 11.2 million shares. Test the hypotheses by constructing a 95 ​% confidence interval. Complete parts​ (a) through​ (c) below. ​(a) State the hypotheses for the test.

Answer 1

Hypothesis: Vs  

Since , the population standard deviation is unknown.

Therefore , use t-distribution.

df=degrees of freedom=n-1=40-1=39

Now , ; The Execl function is , =TINV(0.05,39)

Therefore , the 95% confidence interval is ,

Here , the value 35.1 does not lies in the confidence intervl.

Therefore , reject Ho.

Conclusion : Hence , the stock analyst believes that the stock volume in 2014 is different from the 2011 level.