The average salary of senior managers in the construction industry is $180,000 per year. Suppose we would like to take a sample of senior managers at a newly established company XYZ to see whether the mean annual salary is different from that of the industry.
a) State the null and alternative hypotheses.
b) suppose a sample of 40 senior managers at XYZ showed a sample mean annual salary of $170,000. Assume a population standard deviation of $30,000 with a = 0.05 as the value of significance, what is your conclusion?
Need to know whether this is a one tailed or two tailed step and how do you know that?
Need step by step breakdown so I can follow and study for exam please.
The time needed to drive from city A to city B is normally distributed with a mean of 180 minutes and standard deviation of 20 minutes.
a) what is the probability that a person will drive from city a to city b in three hours or more?
b) what is the probability that a person will drive from city a to city b in more than 140 minutes?
c) what is the probability that a person will drive from city a to city b in exactly three hours?
d) what is the probability that a person will drive from city a to city b in less than 2.5 hours?
Please answer with step by step directions and state formula being used.
In an effort to estimate the mean annual amount spent per customer for groceries at a particular supermarket data were collected for a sample of 100 households. The sample showed an average amount of $8,000. If the population standard deviation is $500,
a) develop an 80% confidence interval estimate of the population mean annual amount spent
b) develop an 85% confidence interval estimate of the population mean annual amount spent
c) if the data were collected for a sample of 50 households rather than 100, develop an 85% confidence interval estimate of the population mean annual amount spent, assuming the population has a normal probability distribution.
what does is mean a normal probability distribution and how is it different from part a) and b).