Unit 3 Flashcards
What are examples of parametric tests?
-F ratio-test (Bartlett’s test)
-1 sample t-test
-Paired t-test
-2 sample t-test
-One-Way ANOVA
-Factorial DOE with one factor and one blocking variable
What are examples of non-parametric tests?
-Leven’s Test
-1 sample sign
-1 sample Wilcoxon
-Mann-Whitney test
-Kruskal-Wallies
-Mood’s median test
-Friedman test
How do you calculate the standard error of the mean (SEOM)?
Standard deviation / square root of sample size
What is the recommended minimum sample size for t-tests to run properly?
When sample sizes are greater than 30
When do you use a z-test?
When sample sizes are greater than 100
What does a One sample t-test do?
Assesses whether the sample (one sample) mean differs significantly from a particular value (Usually a theoretical value)
When is an independent sample t-test used?
When there are two means and two groups that are independent of one another
When is pooled independent t-tests used?
When equal variance is assumed
When is non-pooled independent sample t-tests used?
When unequal variance is assumed
When is paired t-tests used?
-Dependent data (related samples)
-Before and after experiments on the same dataset
What is the p-value for significance?
<0.05
What is the p-value for highly-significant?
<0.01
What is the p-value for very high level of significance?
<0.001
What is the probability of 5% significance of being wrong?
Less than 1 in 20 chance of being wrong
What is the probability of 1% significance of being wrong?
Less than 1 in 100 chance of being wrong
What is the probability of 0.1% significance of being wrong?
Less than 1 in 1000 chance of being wrong
What does a one-tailed directional hypothesis predict?
Predicts the nature of the effect of the independent variable on the dependent variable.
What is an example of a one-tailed directional hypothesis?
In whether the levels of pollution are significantly larger than a maximum threshold marked by legislation.
What does two tailed non-directional hypothesis predict?
-Predicts that the independent variable will have an effect on the dependent variable, but the direction of the effect is not specified
What is an example of a two tailed non-directional hypothesis?
Whether differences in temperature are significantly different either above or below a certain value
What does the left tail in a one tail hypothesis predict?
-Looks for a negative effect
-Whether there is a reduction in the number species / individuals etc
What does the right tail of a one-tailed hypothesis predict?
-Looks for a positive effect
-Whether there is an increase in number of species/ individual etc.
How is the significance level distributed in a two-tailed test?
-Half in left and right tail
-Left 0.025
-Right 0.025
-Makes two tailed tests less powerful than one-tailed t-tests
How is Cohen’s effect size calculated?
CES = Mean difference (mean of group 1 - mean of group 2) / standard deviation
