Complete question :
The average daily volume of a computer stock in 2011 was p = 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 40 trading days in 2014, he finds the sample mean to be 30.9 million shares, with a standard deviation of s = 11.8 million shares. Test the hypotheses by constructing a 95% confidence interval. Complete parts (a) through (c) below. State the hypotheses for the test. Construct a 95% confidence interval about the sample mean of stocks traded in 2014.
Answer:
H0 : μ = 35.1 ;
H1 : μ < 35.1 ;
(26.488 ; 35.312)
Step-by-step explanation:
The hypothesis :
H0 : μ = 35.1
H1 : μ < 35.1
The confidence interval :
Xbar ± Margin of error
Xbar = 30.9
Margin of Error = Zcritical * s/sqrt(n)
Zcritical at 95% = 1.96
Margin of Error = 1.96 * (11.8/sqrt(40))
Margin of Error = 4.412
Lower boundary :
30.9 - 4.412 = 26.488
Upper boundary :
30.9 + 4.412 = 35.312
Confidence interval = (26.488 ; 35.312)
Since the population mean value exists within the interval, the we fail to reject the Null.
