The average age of a vehicle registered in the united states is 8 years, or 96 months. assume the standard deviation is 16 months. if a random sample of a group of 48 vehicles is selected find the probability that the mean of the groups age is between 90 and 100 months.

0.245

Step-by-step explanation:

In order to find find the probability that the mean of the groups age is between 90 and 100 months, we have to find z  for each value

Z = (x – mean)/standard deviation

Le x be the average age of a vehicle

Z1 = (90 – 96)/16 = -0.375

Z2 = (100 – 96)/16 =  0.25

Then we use the z table to find the area under the curve.

Area for Z1 = 0.354

Area for Z2 = 0.599

The probability that the mean of the groups age is between 90 and 100 months can be found as follows:

0.599 – 0.354 = 0.245

b

step-by-step explanation:

introduction, methodology, results, discussion

step-by-step explanation:

an observational study is one which consists of actual observation to record data and then analyse the data.

there are a number of factors that should be analyzed before starting an observational study.

the main four factors are:

i) introduction:   this should be analysed to check whether the purpose of the study is correctly established and the data recorded are appropriate for the study

methodology:   the method of collecting the data, such as whether randomly selected, and whether sample size matches with the population to be studied, whether questions asked are easy to answer by common men, etc.

results: then results such as summary of data with comments should be studied thoroughly

discussion:   the last is the discussion, this can be either by management people or persons who are all interested , etc.