Data distribution Flashcards
How will a histogram look with more variation?
Wider histogram
What are the 3 distribution skews for histograms?
Negative, positive and normal distribution
How will a negative skew look?
Bump to right
How will a positive skew look?
Bump to left
What do histograms show?
A probability distribution
What is the area underneath a histogram equal to?
1, or 100%
What are other names for normal distribution?
Gaussian or symmetrical
What relationship does a normal histogram distribution show about a variable and the mean?
The distribution of a variable within a population is symmetrical about the mean
How do the measures of central tendency look in normal histogram distribution?
Mean = median = mode
What s.d. does a small, pointy normal distribution show?
Smaller standard deviation
What s.d. does a larger, wider normal distribution show?
Larger standard deviation
What must you remember about normal distribution?
For a normal distribution, the proportion of values of a variable within any range can be calculated using the mean and the standard deviation.
What must you remember about normal distribution?
For a normal distribution, the proportion of values of a variable within any range can be calculated using the mean and the standard deviation.
68% values lie…
+/- 1 standard deviation
from the mean
So 34% is 1 s.d. on one side.
95% values lie…
+/- 1.96 standard deviations
from the mean
So 47.5% is 1.96 s.d. on one side.
99% values lie…
+/- 2.6 standard deviations
from the mean
So 49.5% is 2.6 s.d. on one side.
99.7% values lie…
+/- 3 standard deviations
from the mean
So 49.85% is 3 s.d. on one side.
What is the Z-score?
The number of standard deviations a value is away from the mean
What can a Z-table tell you?
The proportion of values that are less than X, based on the Z-score calculated using the formula
