Week 3: scientific method and descriptive stats

The scientific method

Descriptive statistics

Summarises the mid-point and spread of data

Inferential statistics

Identify significant differences/relationships in data

Measures of central tendency

Mode, median, mean

What kind of data should the mode be used for

nominal

What kind of data should the median be used for

ordinal

What kind of data should the mean be used for

interval and ratio

Measures of dispersion

Range, Interquartile range, Standard deviation, Variance

Experimental variance/ between groups variance

The difference between two groups (comes from manipulating variables)

Random variance/within groups variance

Spread of data within the group (random as we don’t know why participants have different scores)

What is a type 1 error

Don’t accept a null hypothesis so accept the alternative, but there is no existing effect at the population level (false positive)

What is a type 2 error

Accept null hypothesis when there actually is a significant difference at the population level

The probability of a type 1 error having occurred

What does statistical significance actually tell us

.05 (5%)

What is the alpha level typically used in psych research

No

If the observed p value is greater than the alpha value is the result significant?

Bimodal (2 modes) or multimodal (more than 2 modes)

What is it called when a data set has multiple peaks

Within group variance

The difference in scores across participants doing the same condition

The difference in scores between conditions

Between group variance

If there is a lot of between group variance and less within group, a result is more likely to be significant. The result may be caused by high within group variance there is no significant difference between conditions as it can be explained by random variance

How are significant results related to between group and within group variance