inferential statistics

Question 1

what are inferential statistical tests?

Answer 1

• Tests based on the mathematics of probability, they help researchers decide how likely a hypothesis is to be true, given the results from a study. They test the null hypothesis.
• Statisticians have produced tests and critical value tables which are used to claim a certain level of certainty that the results are not a chance finding (fluke)
• Psychologists have agreed to use the probability value of p<0.05, which means the probability the results are due to chance at 5% or less

Question 2

what is nominal data?

Answer 2

data is in seperate categories

Question 3

what is ordinal data?

Answer 3

data is ordered - differences between them may not necessarily be the same

Question 4

what is interval data?

Answer 4

data is measured using units of equal intervals (e.g. height measured in centimetres)

Question 5

name the inferential statistical tests

Answer 5

• chi squared test
• mann whitney
• wilcoxon
• spearman’s rank/rho

Question 6

when do you use chi squared?

Answer 6

• testing to see if there is a difference between two or more groups (test of difference)
• gathered nominal data
• used an independent groups design (pps do only one condition each)

NICK IS COOL

Question 7

when do you use mann whitney?

Answer 7

• Testing to see if there is a difference between two or more groups
• Gathered at least Ordinal or higher data (Interval/ratio data)
• Independent Measures design (pps do only ONE condition each)

Ollie Is Messy

Question 8

when do you use wilcoxon?

Answer 8

• Testing to see if there is a difference between two or more groups
• Gathered at least Ordinal or higher data (Interval/ratio data)
• used a repeated measures design

Ollie Runs Wild

Question 9

when do you use spearman’s rank/rho?

Answer 9

• testing to see if there is a relationship between two or more groups
• gathered at least Ordinal or higher data (Interval/ratio data)
• looking for a correlation

(WHEN RANKING, LOWEST GETS NUMBER 1)

Question 10

how do you calculate mann whitney?

Answer 10

• Rank all scores together, ignoring which group they belong to. The lowest score gets a rank of “1”, the next lowest gets a rank of “2”, and so on. If two or more scores are identical, this is a “tie”. They get the average of the ranks that they would have obtained, had they been different from each other.
• Add up the ranks from group a (𝚺) and do the same for group b
• Complete the formula for each group to calculate Ua and Ub
• Compare the smaller of the two U values to the critical value to see if the results are significant - make sure you use the correct table based on whether the hypothesis is one or two tailed and your p value (0.05 or 0.01 etc.) The calculated U value, must be equal to or less than the critical value for the results to be significant.

Question 11

what is a type 1 error?

Answer 11

accepting the alternative hypotheses when the results are actually due to chance (false positive)

Question 12

what is a type 2 error?

Answer 12

accepting the null hypothesis when the results were not due to chance (false negative)