Week 2 Flashcards
What does the mean measure ?
the mean measures central tendency
What occurs when we add and multiply the mean by k ?
- new mean = old mean + k
- new mean = old mean * k
What does SD measure ?
The SD measures the variability
What occurs when we add and multiply to the SD ?
- New SD = old SD
- New SD = old SD * k
What is the null hypothesis ?
predicts that no difference exists between the 2 groups being compared
What is the alternative hypothesis ?
the research hypothesis, which predicts that there is a significant difference existing between the 2 groups being compared
What is a one-tailed hypothesis ?
Directional, in which the alternative hypothesis predicts the direction of the expected difference between the groups
What is a two-tailed hypothesis ?
Non-directional, in which the alternative hypothesis is that a difference exist between groups, but it does not predict the direction of the difference
What is Type I error ?
the error in hypothesis testing in which we rejected a true null hypothesis
What is a Type II error ?
the error in hypothesis testing in which we failed to reject a null hypothesis
What is statistical significance ?
when the observed difference between two descriptive statistics is unikely to have occured due to chance
What is a z-test ?
a parametirc inferential statistical test of the null hypothesis for a single sample where the population variance is known
What is a sampling distribution ?
A distribution of sample means based on random samples of fixed size from the population
What is the central limit theorem ?
Regardless of the shape of the parent populaiton, the random sampling distribution of the sample means tends towards normal, and this tendency towards normal increases with the sample size (N)
What is the standard error of the mean ?
the SD of the sampling distribution
What are the assumptions of z-tests ?
- The sample must be drawn randomly with replacement
- The sampling distribution is normal
- Z-tests require we know the SD of the population
- The sample size must be relatively large (>30)
What is a t-test ?
is parametric inferential statistical test of the null hypothesis for a single sample where the population variance is not known
What is a student’s t-distribution ?
A set of distributions that, although symmetrical and bell shaped, are not normally distributed
What are degrees of freedom ?
The number of scores in a sample that are free to vary
What are the benefits of a t-test over a z-test ?
- Does not require we know the SD of the population
- The n of the sample could be large or small
What are the assumptions of a t-test ?
- The sample was drawn randomly with replacement
- The sampling distribution is symmetrical and bell-shaped
What is effect size ?
The proportion of variance in the dependent variable that is accounted for by the manipulation of the independent variable
What is Cohen’s d ?
An inferential statistic for measuring effect size when using a t-test
What is a independant samples t-test ?
A parametric test that compares the performance of two different sample of participants
