When is the mean, median, and mode the same?
When the data spread is symmetrical (bell curve)
Identify measures of central tendency
Mean, median, mode
Identify measures of spread
Range, Standard Deviation
Identify a weakness of using the range
Doesn’t always change for distributions of different shapes
Identify the three types of variables
1) Non-numerical/Categorical
2) Numerical - continuous (e.g height)
3) Numerical - discrete (e.g siblings)
Define population parameter
A quantity describing some characteristic of a population with respect to a specific variable
Define sample statistic
A quantity describing some characteristic of a sample with respect to a specific variable
Identify the difference between population and sample
Population refers to all members in the world of a category, whereas a sample is a selection of that population
Define deviation
A signed distance of a score from the mean
Why can’t you use the average deviation as a measure of spread?
Answer is almost always zero because the deviations cancel eachother out
What are the 4 steps of calculating the sample variation?
1) Calculate mean
2) Subtract mean from each datapoint to calculate deviations
3) Square each deviation
4) Sum of squared deviations/(N-1) = sample variance
How do you calculate the standard deviation?
Calculate and square root the sample variance
What do histograms allow us to visualise?
-Extreme data points
-The mode
-How scores are spread out
-How data is distributed
What do box plots allow us to visualise?
-The median
-Spread of the data
-Extreme scores
What do scatter plots allow us to visualise?
Relationships between variables
What do data summaries help us visualise?
-Variability in each conditions
-Used when there is a categorical IV (but can also represent numerical IVs with plots)
-Can be used to make predictions
