probability and significance - A-level

Question 1

probability definition

Answer 1

measure of likelihood that a particular event will occur where 0 indicated statistical impossibility and 1 statistical certainty

Question 2

significance definition

Answer 2

statistical term that tells us how sure we are that a difference or correlation exists. a significant result means that the researcher can reject the null hypothesis

Question 3

critical value definition

Answer 3

when testing a hypothesis, the numerical boundary or cut-off point between acceptance and rejection of the null hypothesis

Question 4

type 1 error definition

Answer 4

incorrect rejection of a true null hypothesis (false positive)

Question 5

type 2 error definition

Answer 5

failure to reject a false null hypothesis (false negative)

Question 6

what is the directional or non directional hypothesis sometimes called

Answer 6

alternative hypothesis

Question 7

what does the null hypothesis state

Answer 7

there is no difference between the conditions

Question 8

how do you determine which hypothesis is correct and therefore if to reject or accept the null hypothesis

Answer 8

statistical tests

Question 9

how do statistical test work

Answer 9

based of probability rather than certainty so show a significance level

Question 10

what is the significance level

Answer 10

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 (if the null hypothesis can be rejected and alternative hypothesis accepted)

Question 11

what is the usual significance level

Answer 11

0.05 or (5%)

Question 12

how is the significances level written

Answer 12

p<_ 0.05

Question 13

what does level of significance mean

Answer 13

the probability of the observed effect occurred when there is no effect in the population is equal to or less than 5%. this means when a researcher has claimed to found a significant difference or correlation there is still up to a 5% chance that isn’t true for the target population form which the sample was drawn

Question 14

why can psychologists never be 100% certain about a particular result

Answer 14

haven’t tested all members of the population under all possible circumstances, so have settled on a conventional probability where they are prepared to accept the results may have occurred by chance

Question 15

what happens once the calculated value is decided

Answer 15

checked for statistical significance so calculated value is compared with the critical value which shows if we can reject null hypothesis and accept alternative hypothesis

Question 16

how is a table of critical values used

Answer 16

each stat test has its own table of critical values and for some tests the calculated value must be greater than or equal to critical value ans for some it must be smaller than or equal to

Question 17

3 criteria for using critical value tables

Answer 17

-one tailed or two tailed test
-number of participants in the study
-level of significance

Question 18

how is a one or two tailed test used in a critical value table

Answer 18

directional hypothesis is one tailed and non-directional is two-tailed. probability levels double when two-tailed tests are being used as they are a more conservative predication

Question 19

how is number of participants in a study used in a critical value table

Answer 19

usually appears as the N value on the table. for some tests degrees of freedom are calculated instead

Question 20

how is level of significance used in a critical value table

Answer 20

the 0.05 level of significance is the standard level for psychological research

Question 21

what is the usual level of significance

Answer 21

0.05 level

Question 22

when is a more stringent level of significance used

Answer 22

0.01 os used in studies where there may be a cost to human life such as in drug trials or in one off studies where for practical reasons it could not be repeated in the future

Question 23

what happens if there is a large difference between calculated and critical values in preferred dircetion

Answer 23

researcher will check more stringent levels and the lower the p value os, the more statistically significant the result

Question 24

what is a type 1 error

Answer 24

null hypothesis has been rejected and alternative accepted when it should be the other way round, an in reality the null hypothesis is true

Question 25

how is type 1 error often referred to

Answer 25

optimistic error or false positive as researcher claims to have found a significant difference or correlation when one doesn’t exist

Question 26

what is a type 2 error

Answer 26

null hypothesis is accepted when it should have been the alternative hypothesis accepted, and in reality the alternative hypothesis is true

Question 27

what is a type 2 error often referred to

Answer 27

pessimistic error or false negative

Question 28

when are you more likely to make a type 1 error

Answer 28

if significance level is too lenient (too high) such as a 10% not 5%

Question 29

when is it more likely to make a type 2 error

Answer 29

if significance level is too stringent (too low) such as 0.01, as significant values could potentially be missed

Question 30

why do psychologists favour the 5% level of significance

Answer 30

best balances risk of making type 1 or type 2 error

Question 31

what is the R rule

Answer 31

stats test that have the letter R in the name, calculated value must be greater than critical value