Chapter 8 Intro to Hypothesis Testing Flashcards
What does the null hypothesis state (Ho) ?
that in the general population there is no change, no difference, or no relationship. In the context of an experiment Ho predicts that the independent variable (treatment) has no effect on the dependent variable (scores) for the population
What does the alternative hypothesis (H1) state?
that there is a change, a difference or a relationship for the general population. In the context of an experiment, H1 predicts that the independent variable (treatment) DOES HAVE AN EFFECT on the dependent variable
What is the alpha level?
the probability value that is used to define the concept of “Very unlikely” in a hypothesis test
What is the z score?
the z score specifies the precise location of each x value within the distribution. The sign of the z score signifies whether the score is above or below the mean. The numerical value of the z-score specifies the distance from the mean by counting the number of standard deviations between X and mu
How is the z-score calculated?
the z score is calculated by
the sample mean - hypothesized population mean
divided by
standard error between M and mu
What is a type 1 error?
when a researcher rejects a null hypethsis when it is actually true
what is a type II error?
when the researcher fails to reject the null hypothesis that is really false. In a typical research situation, Type II error means that the hypothesis test has failed to detect a real treatment effect.
When is a result statistically significant?
When it is very unlikely to occur when the null hypothesis is true. Thus a treatment has a significant effect if the decision from the hypothesis test is to reject the null hypothesis
What is the effect size?
A measure of the effect size is intended to provide a measurement of a treatment effect, independent of the size of the sample being used.
How is the Cohen’s d measured?
Mean difference / standard deviation
Is the Cohen’s d affected by the size of the treatment?
No. The cohen’s describes the size of the treatment effect and is not influenced by the number of scores in the sample
What is power?
Power of a statistical test is the probability that the test will correctly reject a false null hypothesis. That is, power is, the probability that the test will identify a treatment effect if one really does exist.
does sample size affect power?
Yes, dramatically.
