2.7 lvls of measurement & descriptive stats Flashcards
why are descriptive stats necessary?
to understand, evaluate, and conduct psych research
Name and describe the two types of stats
- Descriptive stats - summaries and describe, central tendency, concrete and known values
- Inferential stats - uses probability to infer conclusions about larger pops from smaller sample of data
what are four types of data?
Nominal, Ordinal, Interval and Ratio
What is Nominal data?
- Categorical
- lowest lvl of info
- data split into cats but don’t know anything about the numerical relationship between the categories
What is Ordinal data?
- Ranked positions in a group
- don’t know anything about interval between those positions
- Non standardized questionaires with single Likert-type items
What is Interval data?
- uses equal units
- distance of scale points is the same across the whole scale
- E.g.: IQ, test scores, temperature
- Can calculate a range of summary stats
What is Ratio data?
- Interval data that has a true zero and can be used in ratios
- e.g. height, weight, duration
- if a negative can be taken, it isnt a ratio
How do we treat Likert scales?
- single item likert score should be treated as ordinal data
- multiple likert scores that are combined may be treated as interval
What type of data is Nominal/Ordinal? what type of data is Interval/ratio?
- Discrete data - can only have fixed number values
- Continuous - can have infinite number of values
What two things do descriptive stats describe?
- Central tendency
- Dispersion
what is central tendency?
what is the most typical/representative score
what is dispersion?
How much do the values vary around the central value
What are three measures of central tendency?
Mean, median and mode
Define mean
The arithmetic average, sum of scored divided by number of scores
Define median
middle value point, point that divides a set of scored into equal halves
define mode
the scored that occurs most frequently
