The owner of a computer repair shop has determined that their daily revenue has

Question

The owner of a computer repair shop has determined that their daily revenue has mean $7200 and standard deviation $1200. The daily revenue totals for the next 30 days will be monitored. What is the probability that the mean daily revenue for the next 30 days will be between $7000 and $7500? Round to four decimal places. 0.8186 0.7333 0.9147 0.2667 A study was conducted to determine if the salaries of librarians from two neighboring cities were equal. A sample of 15 librarians from each city was randomly selected. The mean from the first city was $28, 900 with a standard deviation of $2300. The mean from the second city was $30, 300 with a standard deviation of $2100. Construct a 95% confidence interval for mu_1 - mu_2. Round to the nearest whole number. (- 4081, 597) (-2871, 567) (-3048, 248) (-2054, 238) The grade point averages for 10 randomly selected junior college students are listed below. Assume the grade point averages are normally distributed. Find a 98% confidence interval for the true mean. Round to the nearest hundredth. (0.67, 1.81) (1.55, 3.53) (3.11, 4.35) (2.12, 3.14)

Explanation / Answer

Solution:

= 7200
= 1200

Use a standard normal table to find the following probabilities:


P(7000 < xbar < 7500)

= P( (7000-7200)/(1200/30))< (xbar-)/(/n) < (7500-7200)/(1200/30))
= P(-0.91 < z < 1.37)

= 1 - .1814 - .0853

= .733

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