When a random sample of participants is selected from a population, the sample mean is not expected to be exactly equal to the population mean. On average, the size of the difference between the...

When a random sample of participants is selected from a population, the sample mean is not expected to be exactly equal to the population mean. On average, the size of the difference between the sample mean and the population mean is predicted by __________

a. the standard error of means (SEM)

b. the mean of the population

c. the sample variance

d. the standard deviation of the population