Which one of the following statements is true?

a.

All else being equal, the more the population standard deviation is reduced, the smaller the margin of error.

b.

The margin of error can be reduced by decreasing the sample size.

c.

For a 90% confidence interval, the reliability factor is equal to 1.96.

d.

Similar to the standard normal distribution, allt- distributions have a mean of zero and a standard deviation of one.

e.

None of the suggested answers are correct