Week 2

Question 1

What does the mean measure ?

Answer 1

central tendency
* add K: New mean = old mean + k
* multiply k: New mean = old mean * k

Question 2

What does standard deviation measure ?

Answer 2

measures the variability
* add K: New SD = old SD
* multiply k: New SD = old SD * k

Question 3

What is the null hypothesis ?

Answer 3

predicts that no difference exists between the two groups being compared

Question 4

What is the alternative hypothesis ?

Answer 4

is the research hypothesis which predicts that there is a significant difference existing b/w the 2 groups being compared
* what the researcher wants to support

Question 5

What is a two-tailed hypothesis ?

Answer 5

It is a non-directional in which the alternative hypothesis is that a difference exist b/w groups, but it doesn’t predict the direction of the difference

Question 6

What is a one-tailed hypothesis ?

Answer 6

It is directional in which the alternative hypothesis predicts the direction of the expected difference b/w the groups

Question 7

What is Type I error ?

Answer 7

error in hypothesis testing in which we rejected a true null hypothesis
* ex: there was no actual difference b/w A and B, but we rejected the null and said that there was a difference

Question 8

What is Type II error ?

Answer 8

error in hypothesis testing in which we failed to reject a null hypothesis
* ex: there was a difference b/w A and B, but the data failed to reject the null and we said there was no difference

Question 9

What is statistical significance ?

Answer 9

when the observed difference b/w 2 descriptive statistics is unlikely to have occured due to chance

Question 10

What is alpha level ?

Answer 10

an acceptable probability of observed difference occuring due to chance

Question 11

What is p value ?

Answer 11

the actual probability of type I error in a statistical test

Question 11

What is a z-test ?

Answer 11

It is a parametric inferential statistical rest of the null hypothesis for a single sample where the population variance is known
* compare sample against population

Question 12

What is a sampling distribution ?

Answer 12

A distribution of sample means based on random samples of fixed size from the population

Question 13

What is the central limit theorem ?

Answer 13

Regardless of the shape of the parent population, the random sampling distribution of the sample means will tend towards normal, and this tendency towards normal increases with the sample size (N)

Question 14

What is the standard error of the mean ?

Answer 14

the SD of the sampling distribution

Question 15

What are the assumptions of z tests ?

Answer 15

1. The sample must be drawn randomly with replacement
2. The sampling distribution is normal
3. Z-tests require we know the SD of the population
4. The sample size must be relatively large ( 30 or more )

Question 16

What is a t-test ?

Answer 16

A parametric inferential statistical test of the null hypothesis for a single sample where the population variance is not known

Question 17

What is a student’s t distribution ?

Answer 17

a set of distributions that, although symmetrical and bell-shaped, are not normally distributed

Question 18

What are degrees of freedom ?

Answer 18

the number of scores in a sample that are free to vary
* any single distribution: df = n-1

Question 19

What are the assumptions of t-tests ?

Answer 19

1. The sample was drawn randomly with replacement
2. The sampling distribution is symmetrical and bell-shaped

Question 20

What are the benefits of t-tests over z-tests ?

Answer 20

1. T-tests doesn’t require knowing the standard deviation of the population
2. The n of the sample could be large or small

Question 21

What is effect size ?

Answer 21

The proportion of variance in the dependent variable that is accounted for by the manipulation of the independent variable

Question 22

What is Cohen’s d ?

Answer 22

An inferential statistic for measuring effect size when using a t-test

Question 23

What occurs to the null and alternative hypothesis wen comparing two sample means ?

Answer 23

Now the hypotheses become whether the two sample are the same (null) or not the same (alternative)

Question 24

What is a independent samples t-test ?

Answer 24

A parametric tests that compares the performance of two different sample of participnants

Question 25

What is the standard error of the difference b/w means ?

Answer 25

The SD of the sampling distribution of differences b/w the means of the independent samples in a two sample experiment

Question 26

What are the assumptions for independent samples t-test ?

Answer 26

1. The samples were interval and ratio
2. The samples were drawn randomly with replacement
3. The distributions are normally distributed
4. The samples are independent of each other
5. Homogeneity of variance - the variance in the first sample should be similar to the variance in the second sample

Question 27

What are the issues with independent sample t-tests?

Answer 27

• Results may be influenced by individual difference factors - a type of inherent variance
• To reduce this, we can have studies designed to have dependent-samples

Question 28

What is a dependent samples t-test ?

Answer 28

A parametric test that compares the performance of two related or matched sample of participants
* two samples are connected (either same person at different times or pairs or matched subjects)

Question 29

What is the standard error of the difference score ?

Answer 29

The SD of the sampling distribution of differences b/w the means of dependent samples in a two-sample study

Question 30

What are the assumptions of dependent samples t-test ?

Answer 30

1. The samples were interval or ratio
2. The samples were drawn randomly with replacement
3. The distributiond are normally distributed
4. The samples are NOT independent of each other
5. Homogeneity of variance

Question 31

What are the pros and cons of dependent tests ?

Answer 31

Pros
* reduced inherent variability

Cons
* Fatigue effect
* Carry-over effect
* Practive effect