Inferential statistics Flashcards
Inferential statistics
IS use the data collected from the collected from the sample to make inferences (assumptions) about the behaviour of the entire target population
Probability
A numerical measure of the likelihood or chance that certain events will occur
Significance
If the result of a statistical test is significant it is highly unlikely to have occurred by chance.
What is the standard level of significance
P is less than or equal to 5%
Significance level
The level of probability at which it has been agreed to reject the null hypothesis
Statistical tests
Mathematical tools researchers use to determine if the results are significant
What are the 3 things do we need to know in order to pick a stats test (explain each one)
Difference or correlation - if it uses the words correlation or relationship it is correlation. If it says effect, difference or words like most/less e.t.c it is a difference
Experimental design - if it is an independent measures (unrelated design) as the two groups were different. If it is repeated measures and matched pairs (related design) as the group is either the same, or been matched
Level of measurement - in both correlational and difference study, we need to know the level of data. Is it nominal ordinal or interval
Interval data (include examples)
Interval scales are precise due to having the same distance (equal intervals) between each adjacent point in standardised scale
Continuous; the value recorded could be any point on the scale used
e.g weight in grams, length in mm, temp in Celsius and time in seconds
Nominal data (include examples)
Often referred to as categorical data, the frequency count of a particular variable is recorded at this level of measurement
e.g country of birth, career choice and taste in music
Ordinal data (include examples)
It has the same properties as nominal data (categorial data) however the categories have a natural order. The difference between each point in an ordinal scale is not inconsistency
e.g include positions in a competition (1st, 2nd, 3rd). Choices on a Likert scale (e.g how happy do you feel 1-7) and relative height among a group of people (tall, medium, tall to smallest)
Draw out the ‘choosing a statistical test’ table
xxx Test of difference Test of association
or correlation
Unrelated design Related design
Nominal data Chi-squared Sign test Chi-squared
Ordinal data Mann-Whitney Wilcoxon Spearman’s rho
Interval data Unrelated t-test Related t-test Pearson’s r
Describe the process of calculating the sign test in finding out whether the data is significant or not
Take the first column from the second
Positive number = +
Negative number = -
Add up the +’s and -‘s
Pick the smallest number (this is s)
One tailed - directional Two tailed - non directional
N= number of participants
‘the calc value of s must be equal to or less than the critical value at 0.05’
What are the 3 things needed to get the calculated value and the critical value
Type of hypothesis - One tailed or two tailed
Number of participants
Level of significance - usually less than or equal to 5%
Type 1 error
When researchers accept the alternative hypothesis (reject the null) in error,
The data collected has passed the level of significance, but really the findings were due to chance variation
Type 2 error
When researchers reject the alternative hypothesis (accept null) in error,
The data collected has not passed the level of significance, but really the participants not acting as expected is due to chance variation hiding the casual relationship between IV and DV
