A study found that citizens spend on average $1950 per year on groceries with a standard deviation of $100. Assume that the variable is normally distributed.

Question

A study found that citizens spend on average $1950 per year on groceries with a standard deviation of $100.  Assume that the variable is normally distributed.

5.  Identify the population mean.

6.  Identify the population standard deviation.

7.  Find the probability that a sample of 20 citizens will have a mean less than $1800.

8.  Find the probability that a sample of 500 citizens will have a mean greater than $2000.

PsyDAG · Answer

Don't know population mean and SD, but study data is best estimate.

5. $1950

6. $100

7. Z = (score-mean)/SEm

SEm = SD/√n

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.

8. Same process as 7.