PSYCH STATS QUALIFYING EXAM

If the standard deviation of the population is 15 and we repeatedly draw samples of 25 observations each: the resulting sample means will have a standard error of

3

A confidence interval computed for the mean of a single sample

is associated with a probability about the location of a population mean.

For a t test with one sample we

lose one degree of freedom because we estimate the mean.

A 95% confidence interval is going to be _______ a 99% confidence interval.

narrower than

If the population from which we draw very large samples is "rectangular": then the sampling distribution of the mean will be roughly

normal

When we are using a two-tailed hypothesis test: the null hypothesis is of the form

H0 : μ = 50.

When we are using a two-tailed hypothesis test: the alternative hypothesis is of the form

H1 : μ ≠ 50.

When you are using a one-sample t test: the degrees of freedom are

N - 1

A one-sample t test was used to see if a college ski team skied faster than the population of skiers at a popular ski resort. The resulting statistic was t(23) = -1.13, p < .28. What should we conclude?

The sample mean of the college skiers was not significantly different from the population mean.

A one-sample t test was used to see if a college ski team skied faster than the population of skiers at a popular ski resort. The resulting statistic was t(23) = -7.13, p < .05. What should we conclude?

The sample mean of the college skiers was significantly different from the population mean.

All of the following increase the magnitude of the t statistic and/or the likelihood of rejecting H0 EXCEPT

a smaller significance level (alpha).

If we compute 95% confidence limits on the mean as [112.5, 118.4]: we can conclude that

an interval computed in this way has a probability of .95 of bracketing the population mean.

The t distribution

approaches the normal distribution as its degrees of freedom increase.

If we have run a t test with 35 observations and have found a t of 3.60 which is significant at the .05 level: we would write

t(34) = 3.60, p <.05.

If we fail to reject the null hypothesis in a t test we can conclude

that we do not have enough evidence to reject the null hypothesis.

The term "effect size" refers to

the actual magnitude of the mean or difference between means.

An assumption behind the use of a one-sample t test is that

the population is normally distributed

The two-tailed p value that a statistical program produces refers to

the probability of getting at least that large an absolute value of t if the null hypothesis is true.

When you have a single sample and want to compute an effect size measure: the most appropriate denominator is

the standard deviation of the sample.

If the population from which we sample is positively skewed: the sampling distribution of the mean

will approach normal for large sample sizes

If the population from which we sample is normal: the sampling distribution of the mean

will be normal