Chapter 16 Significance Testing - A Real Effect? Flashcards Preview

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Flashcards in Chapter 16 Significance Testing - A Real Effect? Deck (25)
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1

Alpha

Percentage of the probability area under H0 that forms the 'rejection region'; level set for acceptable probability of Type 1 error under H0

2

Beta

If the null hypothesis is not true, this is the probability that a Type 2 error will be made

3

Significance Test/Decision

Test performed in order to decide whether the null hypothesis should be retained or rejected

4

Significance

A significant effect is declared when the probability of the finding occurring under H0 is less than the set level of alpha

5

Inferential Test/Statistics

Procedures for making inferences about whole populations form which samples are drawn. e.g., significance tests

6

Null Hypothesis

Assumption of no effect in the population from which samples are drawn (e.g., no mean population difference or zero correlation)

7

Alternative Hypothesis (H1)

Assumption than an effect exists (e.g., that populations differ or population correlation is not zero)

8

Logical Probability

A measure of probability calculated from logical first principles

9

Probability

A numerical measure of pure 'chance' (randomly based) occurrence of events

10

Empirical

A measure of probability based on existing frequencies of occurrence of target effects

11

Significance Levels

Levels of probability at which it is agreed to reject H0. If the probability of obtained results under H0 is less than the set level, H0 is rejected.

12

Critical Value

Value that the result of the test statistic (e.g. z) must reach in order for the null hypothesis to be rejected

13

Non-Directional Hypothesis

Hypothesis that does not state in which direction a difference or correlation exists

14

Probability Distribution

A histogram of the probabilities associated with the complete range of possible events

15

Rejection Region

Area of (sampling) distribution where, if a result falls within it, H0 is rejected; the more extreme area cut off by the critical value

16

Type I Error

Mistake made in rejecting the null hypothesis when it is true

17

Type II Error

Mistake made in retaining the null hypothesis when it is false

18

Effect Size

The size of the effect being investigated (difference or correlation) as it exists in the population

19

Power

1-Beta. The probability of not making a Type II error if a real effect exists; the probability of obtaining a case or sample statistic above the level cut off by beta in the population defined by the alternative hypothesis.

20

p is less than or equal to .1

Significance level generally considered too high for rejection of the null hypothesis but where, if p under H0 is this low, further investigation might be merited

21

p is less than or equal to .05

Conventional significance level

22

p is less than or equal to .01

Significance level preferred for greater confidence than that given by the conventional one and that should be set where research is controversial or a one-shot-only trial

23

Directional Hypothesis

Hypothesis that states which way a difference or correlation exists - e.g. population mean A > population mean B, or correlation is negative

24

One-tailed test

Test referring to only one tail of the distribution under H0; may be used if the alternative hypothesis is directional (but controversial)

25

Two-tailed test

Test referring to both tails of the probability distribution under H0; must be used if alternative hypothesis is non-directional