Distribution Flashcards
What is a parametric test?
When there are certain features (parameters) that the study has to meet to use one.
Used when the data is NORMALLY distributed.
What is a non-parametric test?
If the data is not normally distributed (positively/negatively skewed)
What are examples of parametric tests?
Related/Unrelated t-tests
Pearson’s r
What are examples of non-parametric tests?
All of them except…
Related/Unrelated t-tests
Pearson’s r
What are the features of a normal distribution?
“Bell” shaped curve.
The mean, median and mode are the SAME value - at the middle of the curve.
Most people in a population fit near to the middle point.
The end bits are called the tails.
What are examples of skewed distributions?
Positively skewed
Negatively skewed
What are the features of a positively skewed curve?
The highest peak is on the LEFT side.
Has a long tail to the right of the peak.
ORDER:
mOde, median, mean
pOsitive means mOde goes first.
Most people have scored LOW on a test/measure.
Positive means the test was hard.
What are the features of a negatively skewed curve?
The highest peak is on the RIGHT side.
Has a long tail to the left side of the peak.
ORDER:
mEan, median, mode
nEgative means mEan goes first.
Most people have scored HIGH on a test/measure.
Negative means the test was easy.
How would you remember the measures of central tendency in a positive and negative skew?
The median is always in the MIDDLE.
The mEan comes first in nEgative.
The mOde comes first in pOsitive.
Negative:
Mean, median, mode
Positive:
Mode, median, mean
Things to remember in a distribution question.
Separates A* students from the rest.
Whenever there is a question asking you to “comment on the data”, and they tell you the averages (mean, median, mode), then ALWAYS refer to the distribution (is it normal, positive or negative).
They might ask you to SKETCH a distribution.
Specify where the mean, median and mode is and whether its normal, positive or negative.
They might ask whether the test was hard or easy.
