Arandom sample of 85 supervisors revealed that they worked an average of 6.5 years before being promoted. the population standard deviation was 1.7 years. using the 0.95 degree of confidence, what is the confidence interval for the population mean? select one: a. 6.99 and 7.99 b. 4.15 and 7.15 c. 6.14 and 6.86 d. 6.49 and 7.49

c. 6.14 and 6.86

Step-by-step explanation:

The confidence interval for population mean is given by :-

, where n= sample size

= Sample mean

= Population standard deviation

z*= Critical z-value.

As per given , we have

n= 85

For 0.95 degree of confidence interval , the critical z-value is 1.96. (By z-table).

So , the required confidence interval will be:

Hence, the confidence interval for the population mean is c. 6.14 and 6.8 .

answer: 7 x 2/5 = 2.8 hours, is your answer. your welcome! : 3

step-by-step explanation: first work out how long it took to hose 1/7 of the lawn which is 2/5 hours. times that by 7 to get the whole lawn.

sorry i don't know the other answer. i didn't learn what a proportional relationship is.