Surgical wounds heal more slowly in people who are stressed. Ten nursing students were given puncture wounds during their exam period and during summer vacation. Their rate of healing was much slower when they received wounds during their exam period.

The following are the number of days it took the 10 nursing students to heal from their wounds during their exam period.

566897810910The mean of this population of numbers is = 7.8, and the standard deviation is = 1.66.

Suppose you take a sample of four of these 10 nursing students. The following are the number of days it took the four students to heal from their wounds during their exam period.

910910

The mean of this sample of numbers is M = , and the standard deviation is s = 0.58.

Suppose you take a sample of eight of the 10 nursing students. The following are the number of days it took the eight students to heal from their wounds during their exam period.

6689781010

The mean of this sample of numbers is M = , and the standard deviation is s = 1.60.

Calculate the standard error of the mean for the sample of four:

M

M= .

Calculate the standard error of the mean for the sample of eight:

M

M= .

The sample of is a better estimate of the population.