Psych Stats test 3

An independent t-test is used to test for:

Differences between means of groups containing different entities when the sampling distribution is normal, the groups have equal variances and data are at least interval.

An paired-samples t-test is used to test for:

Differences between means of groups containing the same entities when the sampling distribution is normally distributed, and the data have equal variances and are at least interval.

Which of the following statements best reflects statistical power?

The ability of a statistical test to detect a difference when one genuinely exists.

independent samples t-test

used when there are two experimental conditions and different participants were assigned to each conditions and different participants were assigned to each condition n-2

When is a number significant?

significant if more than # on table, not significant if less than #

Once you have the significance value of the t-test, it is beneficial to calculate the effect size. Cohen's d is a measure of effect size. How is it calculated?

(mean 2 - mean 1) / mean of the standard deviation

Suppose we wanted to apply a one-tailed test as opposed to a two-tailed test. How would we covert a significance of p = .284?

.284 / 2 = .142

Which of the following statements about the t distribution is correct?

As the degrees of freedom increase, the distribution becomes closer to normal

homework question

If number is more than what is on the chart it is not significant

Which of the following t-tests has a different research design?

Independent t-test

The t-statistic

Is the ratio of the systematic variation to the unsystematic variation.

A recent study investigated whether vodka is less likely to give you a hangover than wine. Twenty participants on a night out were asked to drink only vodka for the whole evening then rate how they felt the next day out of 10 (0 = I feel fantastic, 10 = I can't move my head in case it explodes). The following month, they were asked to do the same again, only this time they were asked to drink only white wine. The t-score was 2.56. Which of the sentences below is correct? (Hint: You will need to look up the p-value in the table of critical values of the t-distribution in the Appendix.)

It is significant at the 5% level but not the 1% level with a two-tailed test.

Which of the following sentences is an accurate description of the standard error?

It is the standard deviation of the sampling distribution of a statistic.

How is a t-statistic calculated?

Mean difference / standard error of the mean

Which of the following is not a form of t-test?

Mixed model t-test

The degrees of freedom for the paired samples t-test are:

N − 1

Consider an independent t-test. Which of the following expressions best represents the degrees of freedom?

N-2

A researcher measured a group of people's physiological reactions while watching horror films and compared them to when watching comedy films. The resulting data were normally distributed. What test should be used to analyse the data?

Paired-samples (dependent or related) t-test

What does the independent t-test test assume?

The sampling distribution is normally distributed

When conducting an independent t-test, what is the dependent variable?

The scores

Two samples of data are collected and the sample means calculated. If the samples come from the same population, then:

Their means should be roughly equal.

Cohen's D

d= mean 1-mean 2/ baseline standard deviation

levene's test

if less than .05 then variance is not the same

If a significance result of .000 is presented, how should this be reported?

p < .001

paired samples t-test

this test is used when there are two experimental conditions and the same participants took part in both conditions of the experiment n-1