Question

The average daily volume of a computer stock in 2011 was

muμequals=35.1

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

30

trading days in​ 2014, he finds the sample mean to be

31.7

million​ shares, with a standard deviation of

sequals=12.5

million shares. Test the hypotheses by constructing a

95 %

​(b) Construct a

95%

confidence interval about the sample mean of stocks traded in 2014.The lower bound is

nothing

million shares.

The upper bound is

nothing ?

million shares.

Answer 1

H0: = 35.1

Ha: 35.1

Test statistics

t = - / S / sqrt(n)

= 31.7 - 35.1 / 12.5 / sqrt(30)

= -1.49

t critical value at 0.05 level with 29 df = -2.045 , 2.045

Since test statistics falls in non-rejection region , Do not reject H0

b)

95% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

31.7 - 2.045 * 12.5 / sqrt(30) < < 31.7 + 2.045 * 12.5 / sqrt(30)

27.03 < < 36.37

Lower bound = 27.03

Upper bound = 36.37