Types of Distribution. Flashcards
What shape is a normal distribution curve?
A bell shape.
The Normal Distribution Curve plots a _____ distribution of values.
Normal.
What is a characteristic of the Normal Distribution Curve (think symmetry).
It is symmetrical about the mid point of the horizontal axis.
The symmetrical point of a Normal Distribution Curve is where what?
Where the mean, median and mode fall in the distribution.
What do the tail ends of the distribution never quite meet?
They never quite meet the horizontal axis.
Where is the area of the normal distribution curve contained?
Between the mean in the centre and the point where one standard deviation falls on the distribution.
When we say that our variables are normally distributed, what do we mean by this?
We mean that they are close approximations to this normal curve.
What do statistics normally assume?
They assume that the values are normally distributed.
If the distribution is nothing like the normal one, what can this lead to?
This can lead to erroneous conclusions.
- Interval scales use equal units
- Distance between values are the same
- Does this apply to psychological scales?
Yes, if they are standardised.
On a standardised scale, what does this mean?
The distance between the points are equal.
Test creators use their knowledge of the properties of a normal distribution to ____________ their Psychological Scales.
Standardise.
What does a standardised psychological scale ensure?
That the test produces the same proportions of people along the points of a scale.
Height is an example of a _______ _______ curve.
Normal Distribution.
What level do unstandardized scales operate at?
Ordinal Level.
Standardised scales operate at ______ level.
Interval.
IQ scale is also _______.
Standardised.
What do standardised scales have?
Normal Distribution.
Not all distributions are normal, what are these called?
Skewed Distributions.
What are skewed distributions described as being?
Lopsided.
Why is the type of distribution (normal or skewed) important?
The shape determines which central tendency and dispersion will best describe the distribution.
What curve plots a normal distribution of values?
The Normal Distribution Curve,
Skewed distributions are _______. Where do they have their peak?
Lopsided.
They have their peak to one side.
Skewed distributions have their peak to one side, what does this mean?
The mode is to one side.
Skewed distributions have a ____ on one side where more than _____ the values occur.
Tail, Half.
In a negatively skewed distribution, where do most of the values get clustered?
Around the top end of the distribution.
Extroversion can be an example of a ______ or ________ skewed distributions.
Negatively, Positively.
If mean is high, what happens?
People cant score much higher than the mean but lots of people can still score much lower than the mean.
In skewed distributions, a greater number of values below the mode, does what?
Shifts the mean towards the tail.
The mean gets pulled in the direction of ______.
skew.
Where does the median line sit in skewed data?
Between the mode and mean.
The _____ is most sensitive to extreme values.
Mean.
In skewed distribution, what are the better measures of central tendency?
Median (or mode, but median is better than mode).
If the mean is low, and the data is clustered at the bottom of the graph, what is this known as?
Positively Skewed Distribution.
In positively skewed distribution the mean is _____.
Low.
When the mean is low, most people can’t score much _____ but a significant amount can still score much __________.
lower, higher.
What could reaction time be an example of?
A positively skewed distribution.
In the graph, what does the highest point mean?
It is the mode- aka. the most frequently occurring number.
In a positively skewed distribution, what way is the mean pulled?
It is pulled to the right (in the direction of skew).
In skewed data what sits in the middle of the mode and mean?
The median.
For skewed data what is the best measure of central tendency to use?
Median.
In both types of skew, what is furthest from the mode?
The mean.
In negative skew the mean is _____ than mode.
less.
In positive skew the mean is ______ than the mode.
Greater.
What will Parametric stats assume?
That the data is from a normal distribution.
How do we determine whether data is screwed or not?
Look at mean and median of data and if they are half a standard deviation or more apart then the data is skewed.
If the mean, mode and median are all the same the data is ______ distributed.
normally.
If there is a difference between the mean, mode and median, data could be ______.
Skewed.
In order to determine skew, look at the size difference between ____ and ______, compare this difference to half of the ______ ________.
Mean, Median, Standard Deviation.
if skewed distribution in interval or ratio data what measures of dispersion must we use?
Range, IQ range or semi-IQ range.
For normally distributed interval or ratio data, what measure of dispersion do we use?
Standard Deviation.
In normal distributions what is equal? And what is the most appropriate measure of central tendency?
Mean=Mode=Median
The mean.
A characteristic of skewed distribution is that what?
The mean, median and mode don’t lie in the same place.
What 3 pieces of information do we use to describe a data set?
- Type of Distribution
- Measure of Central Tendency
- Measure of dispersion.
