Week 5: Comparing Means: Independent and Paired T-test Flashcards
What are the 3 types of t-tests? - (3)
- One-samples t-test
- Paired t-test
- Independent t-test
Whats a one-sample t-test?
Compares the mean of the sample data to a known value
What is the assumptions of one-sample t-test? - (4)
- DV = Continous (interval or ratio)
- Independent scores (no relation between scores on test variable)
- Normal distribution via frequency histogram (normal shape) and Q-plot (straight line) and non significant Shaprio Wilk
- Homogenity of variances
Example of one-sample t-test RQ
Is the average IQ of Psychology students higher than that of the general population (100)?
What is the assumptions of independent samples t-tests (listing all of them) - (7)
- Independence. – no relationship between the groups
- Normal distribution via frequency histogram (normal shape) and Q-plot (straight line) and non significant Shaprio Wilk
- Equal variances
- Homogeneity of variances (i.e., variances approximately equal across groups) via non significant Levene’s test
- DV = Interval or continuous
- IV = Categorical
- No significant outliers
What is an RQ example of independent samples t-tesT?
Do dog owners in the country spend more time walking their
dogs than dog owners in the city?
What is the assumptions of paired t-test? (listing all) - 3
DV is continuous
Related samples: The subjects in each sample, or group, are the same. This means that the subjects in the first group are also in the second group
Normal distribution via frequency histogram (normal shape) and Q-plot (straight line) and non significant Shaprio Wilk
What is an example of RQ of paired t-test?
Do cats learn more tricks when given food or praise as positive feedback?
What is the decision framework for choosing a paired-sample (dependent) t-test? - (5)
- What sort of measurement = continous
- How many predictor variables = one
- What type of predictor variables = categorical
- How many levels of categorical predictor = two
- Same or different participants for each predictor level = same
What is the decision framework for choosing independent-t-test? (5)
- What sort of measurement = continous
- How many predictor variables = one
- What type of predictor variables = categorical
- How many levels of categorical predictor = two
- Same or different participants for each predictor level = different
If we are comparing differences between means of two groups in independent/paired t-test then all we are doing is
predicting an outcome based on membership of two groups
Indepdnent and paired t-tests can fit into an ideal of a
linear model
What is coding with dummy variables and an example?
E.g., coding absence of cloak in terms of numbers (like 0) and pps with clock as 1 even though it is a categorical variable
Independent and paired t-tests (comparing difference of two means) fit into idea of general linear model
What does b0 and b1 represent in this general linear model? - (2)
*b0 is equal to the mean of group coded as 0 (in this case no cloak)
* b1 is difference between group means
The t-distributed is defined by its
degrees of freedom - related to the sample size.
The t distribution has heavier tails for
lower degrees of freedom (small N studies)
What are the two different t-tests? - (2)
- Independent-means t-test
- Dependent-means test
Independent and Paired T-tests have one predictor (X) variable with 2 levels and only …. outcome variable (Y)
one
When is an independent-means t-test used?
When 2 experimental conditions and different participants are assigned to each condition
What is independent-means t-test sometimes called as well?
independent-samples t-test
When is a dependent-means t-test used?
Used when there are 2 experimental conditions and same participants took part in both conditions of the experiment
What is dependent-means t-test sometimes referred to?
Matched pairs or paired samples t-test
For independent and paired t-tests we compare between the sample means that we collected to the difference between sample means that we would expect if
there was no effect (i.e., null hypothesis was true)
In independent and paired t-tests if standard error was small then suggests that sample means of two groups are quite
similar