Descriptive and Inferential Statistics

Question 1

What 2 characteristics of data most need to be summarised?

Answer 1

• central tendency

- dispersion

Question 2

What is a z score and how is it calculated?

Answer 2

• z-score is the number of standard deviations any particular score is away from the mean
• (score-mean)/SD where score = zSD + mean

Question 3

According to the central limit theorem, what 3 characteristics will be present in normally distributed data?

Answer 3

• Distribution of all sample means (sampling distribution) will approach a normal distribution
• Mean of all sample means will equal the mean of the population
• As the sample size increases standard deviation of the sampling distribution decreases

Question 4

Define population mean

Answer 4

The mean of the sample means

Question 5

What is standard error and how is it calculated?

Answer 5

= standard deviation/square root of the number of scores

Question 6

What is inferential statistics?

Answer 6

Statistics that allow us to make an inference/generalisation about the population from which our samples are drawn

Question 7

What is a type 1 and type 2 error?

Answer 7

type 1 - reject null hypothesis when it is true

type 2 - accept null hypothesis when it is false

Question 8

What are the parametric assumptions of a t-test?

Answer 8

data is interval/ratio
distribution is normal
homogeneity of variance

Question 9

What is a t-distribution?

Answer 9

• when working on smaller sample sizes assume t-distribution rather than normal distribution
• shape is dependent on degrees of freedom

Question 10

In what 2 situations would you use a t-test?

Answer 10

• drawn from a population whose mean is known

- two sets of measurements are drawn from the same population

Question 11

Define the t value

Answer 11

the difference in means/variability about means

Question 12

What is a single-sample t-test and how are the degrees of freedom calculated?

Answer 12

• tests whether a sample mean is significantly different from a known population mean
• df = n(1) -1

Question 13

How do you report a single samples t-test?

Answer 13

t (df) = (t-value), p= (p value)

Question 14

What is a paired samples t-test and how are dregrees of freedom calculated?

Answer 14

• tests if means of sample differ from before and after an intervention
• df = n(1) - 1

Question 15

What is the formula for a paired samples t-test?

Answer 15

t = (mean differences of scores) / (standard deviation of differences in scores/square root of number of particpants)

Question 16

What kind of data is SPSS mainly used for?

Answer 16

inferential statistics

Question 17

What’s the difference between within subject test and between subject test?

Answer 17

Data gathered from the same people = within-subjects. Comparisons are made within the same people

Data gathered from different people = between-subjects. Comparisons are made between different people.

Question 18

What is the function to calculate mean in excel?

Answer 18

=AVERAGE(

Question 19

What is the function to calculate standard deviation in excel?

Answer 19

=STDEV(

Question 20

What is the variance of certain data set in excel?

Answer 20

standard deviation

Question 21

For neighbour columns, SPSS can only deal with within or between subject test?

Answer 21

within subject test.

between subject test should be put in separate rows

Question 22

what are the two t-tests that excel can run?

Answer 22

paired- and independent-samples t-tests.

It will only give you the p-value (significance) of the t-test, not the t-statistic or the degree of freedom.

Question 23

what is independent-samples t-test

Answer 23

The Independent Samples t Test compares the means of two independent groups in order to determine whether there is statistical evidence that the associated population means are significantly different.

Question 24

what is paired-sample t-test

Answer 24

The paired sample t-test, sometimes called the dependent sample t-test, is a statistical procedure used to determine whether the mean difference between two sets of observations is zero. In a paired sample t-test, each subject or entity is measured twice, resulting in pairs of observations.

Question 25

what is the function of t-test in excel?

Answer 25

=TTEST(array1,array2,tails,type) array1 is the first dataset array2 is the second dataset tails specifies the number of distribution tails (1 = one-tailed, 2 = two-tailed) type is the kind of t-test to perform (1 = paired, 2 = independent, equal variance-assumed, 3 = independent unequal variance-assumed)

Question 26

what is the difference between one-tailed and two tailed hypothesis?

Answer 26

one-tailed hypothesis predict a direction of the difference (larger or smaller) while two tailed hypothesis does not

Question 27

how many decimal place should be reported for p value in exam?

Answer 27

3

Question 28

how to interpret p value

Answer 28

If it is less than .05, the test is significant, if it is greater than .05, it is not.

Question 29

when do we use paired-sample t-test?

Answer 29

if you are comparing two measurements from the same sample, you are using a paired samples t-test.

Question 30

when do we use independent-sample t-test?

Answer 30

if you are comparing two different samples, you are using a independent-sample t-test.

Question 31

when do we have equal variance-assumed or variance-assumed when doing independent-sample t-test in excel?

Answer 31

we don’t have the capacity to test the equal variances assumption in Excel, we should go ahead and assume equal variances.

Question 32

how to conclude the data from t-tests?

Answer 32

A paired-samples/independent-samples t-test found a/no significant difference between the scores obtained by (group) (condition) and (group) (condition).

Question 33

How to interpret t-test results in SPSS?

Answer 33

SPSS reports p-values under the heading ‘Sig.’

Question 34

what is Paired Samples Correlation significance

Answer 34

SPSS automatically provides you with a correlation coefficient for the two paired samples and significance value for this correlation in case you are interested in the relationships between performances in Semesters 1 and 2 (in this case, .000). However, this Paired Samples Correlations significance value is not related to our paired samples t-test and should not be reported unless you are reporting the correlation.

Question 35

what is Paired Samples Test significance.

Answer 35

The significance value related to the Paired Samples t-test is the Sig. (2- tailed) value in the Paired Samples Test output that follows the t and df parameters (in this case, .003). This is the p-value you should report in your write-up of the results.

Question 36

can t-value be negative?

Answer 36

T-tests can produce negative t-values as well as positive t-values. The sign (negative or positive) is not important. reporting the t-value as 3.31 would have been just as accurate as reporting it as -3.31.

Question 37

what does Levene’s Test for Equality of Variances mean in interpreting the spss results?

Answer 37

If the significance of the Levene’s statistic is greater than .05, the independent samples have equal variances. If the significance of the Levene’s statistic is less than .05, the independent samples have unequal variances.