Probability and significance

Question 1

How do researchers begin their investigations?

Answer 1

By writing a hypothesis

Question 2

Hypotheses may be what depending on how confident the researcher is in the outcome of the investigation?

Answer 2

Directional or non-directional

Question 3

What is the alternative to a null hypothesis called?

Answer 3

Alternative hypothesis

Question 4

What does the null hypothesis state?

Answer 4

There is ‘no difference’ between the conditions

Question 5

Statistical tests work on the basis of ___________ rather than certainty

Answer 5

probability

Question 6

All statistical tests employ a ____________ level - the point at which the researcher can claim to have discovered a large enough difference or correlation within the data to claim an effect has been found.

Answer 6

significance

Question 7

Significance level

Answer 7

The point at which the researcher can claim to have discovered a large enough difference or correlation within the data to claim an effect has been found

Question 8

The point at which the researcher can reject the null hypothesis and accept the alternative hypothesis is known as…

Answer 8

the significance level

Question 9

What is the usual significance level in psychology?

Answer 9

0.05 (or 5%)

Question 10

How is the usual significance level in psychology properly written?

Answer 10

p ≤ 0.05 (where p stands for probability)

Question 11

The usual level of significance in psychology is 0.05 (or 5%). What does this mean?

Answer 11

Even when a researcher claims to have found a significant difference/correlation, there is still up to 5% chance that it isn’t true for the target population from which the sample was drawn

Question 12

True/False: Psychologists can never be 100% certain about a particular result

Answer 12

True

Question 13

Why can psychologists never be 100% certain about a particular result?

Answer 13

They have not tested all members of the population under all possible circumstances

Question 14

Psychologists have settled upon a conventional level of probability where they are prepared to accept that results may have…

Answer 14

occurred by chance

Question 15

Once a statistical test has been calculated, the result is a number. What is this called?

Answer 15

The calculated value / observed value

Question 16

To check for statistical significance, what must the calculated value be compared with?

Answer 16

A critical value

Question 17

|Critical value

Answer 17

A number that tells us whether or not we can reject the null hypothesis and accept the alternative hypothesis

Question 18

Each statistical test has its own table of ________ ______, developed by statisticians

Answer 18

critical values

Question 19

What are the three criteria needed to know which critical value to use?

Answer 19

Whether its a one or two-tailed test, the number of participants in the study or degrees of freedom and the level of significance/p value

Question 20

When do you use a one-tailed test?

Answer 20

If your hypothesis was directional

Question 21

When do you use a two-tailed test?

Answer 21

If your hypothesis was non-directional

Question 22

Why do probability levels double when two-tailed tests are being used?

Answer 22

They are a more conservative prediction

Question 23

The number of participants in a study usually appears as which value on a table of critical values?

Answer 23

The N value

Question 24

When may a more stringent level of significance such as 0.01 be used?

Answer 24

In studies where there may be a human cost, such as drug trials or ‘one-off’ studies that could not, for practical reasons, be repeated in future

Question 25

If there is a large difference between the calculated and critical values in the preferred direction, what is a researcher likely to do?

Answer 25

Check more stringent levels, as the lower the p value is, the more statistically significant the result

Question 26

A Type I error is when...

Answer 26

the null hypothesis is rejected and the alternative hypothesis is accepted when it should have been the other way around because, in reality, the null hypothesis is 'true'

Question 27

What are Type I errors often referred to as?

Answer 27

An optimistic error or false positive

Question 28

A Type II error is when...

Answer 28

the null hypothesis is accepted but it should have been the alternative hypothesis because, in reality, the alternative hypothesis is true

Question 29

What are Type II errors often referred to as?

Answer 29

Pessimistic errors or false positives

Question 30

When are we more likely to make a Type I error?

Answer 30

If the significance level is too lenient (too high)

Question 31

When are we more likely to make a Type II error?

Answer 31

If the significance level is too stringent (too low)

Question 32

Psychologist favour the 5% level of significance as it best balances the risk of making what?

Answer 32

Type I and Type II errors