Answer:
Given:
Mean, u = 135
Sample size, n = 42
Sample mean, x' = 126
Standard deviation = 16
Significance level = 0.05
1) The null and alternative hypotheses:
H0 : u = 135 (the revenue per day is $135)
H1 : u < 135 (the revenue per day is less than $135)
2) In this case, we have a left tailed test.
Let's use the formula:
![= \frac{x' - u}{s/ \sqrt{n}} = \frac{126 - 135}{16 / \sqrt{42}} = -3.645](https://tex.z-dn.net/?f=%20%3D%20%5Cfrac%7Bx%27%20-%20u%7D%7Bs%2F%20%5Csqrt%7Bn%7D%7D%20%3D%20%5Cfrac%7B126%20-%20135%7D%7B16%20%2F%20%5Csqrt%7B42%7D%7D%20%3D%20-3.645%20)
t = - 3.645
Critical value: at a significance level of 0.05, left tailed test,
tcritical = -1.683
We reject null hypothesis, H0, since t calculated, -3.645 is less than tcritical, -1.683.
3) Given, a = 0.05, df = 41, left tailed test,
t-value = 2.02
For the corresponding confidence interval, we have:
![CI = (x' - \frac{t * \sigma}{\sqrt{n}}, x' + \frac{t * \sigma}{\sqrt{n}})](https://tex.z-dn.net/?f=%20CI%20%3D%20%28x%27%20-%20%5Cfrac%7Bt%20%2A%20%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%2C%20x%27%20%2B%20%5Cfrac%7Bt%20%2A%20%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%29%20)
![CI = (126 - \frac{2.02 * 16}{\sqrt{42}}, 126 + \frac{2.02 * 16}{\sqrt{42}})](https://tex.z-dn.net/?f=%20CI%20%3D%20%28126%20-%20%5Cfrac%7B2.02%20%2A%2016%7D%7B%5Csqrt%7B42%7D%7D%2C%20126%20%2B%20%5Cfrac%7B2.02%20%2A%2016%7D%7B%5Csqrt%7B42%7D%7D%29%20)
CI = (121.014, 130.986)
4) Conclusion:
We reject the estimated potential revenue advised by the consultant, H0, as it is too high, because the t-calculated falls in rejection region(i.e, less than critical value), also the upper limit of the confidence interval is less than $135.