23. RM Distribution and Histograms Flashcards
Describe the presentation of ‘normal distribution’.
-Bell shaped curve.
-Mean, median and mode should be aligned around the mid point.
-Tail ends shouldn’t meet the horizontal axis.
-Symmetrical.
In ‘normal distribution’ what is the relationship between the mean, median and mode?
Mean=Median=Mode
(Either same or similar)
Define a normal distribution of data.
A normal distribution of data means that most the examples in a set of data are close to the average, while relatively few examples tend to one extreme or the other.
What is the purpose of standard deviation?
Standard deviation calculates the distance of a score from its group mean.
In normal distribution, what % of scores lie within + or - 1SD of the mean.
68%
In normal distribution, what % of scores lie within + or - 2SD of the mean.
95%
In normal distribution, what % of scores lie within + or - 3SD of the mean.
99%
Is that that is multi-modal (more than one mode) normally distributed?
No.
When will distribution be skewed?
(Data distributions can be skewed due to extreme values of outliers)
If mean, median and mode are not similar.
Describe a positive skew.
-A positive skew is a skew to the right (the graph has a low tail on the right).
-When: Mode < Median < Mean
(The median is always in the middle of the graph)
Describe a negative skew.
-A negative skew is a skew to the left, the graph has a long tail on the left.
-When: Mean < Median < Mode
(The median is always in the middle of the graph)
Why is the mode always the highest point on the graph?
As it’s the most common value.
Explain why a researcher may choose to use SD over the range to measure dispersion?
A researcher may choose to use SD over the range to measure dispersion as the SD is the most sensitive measure of dispersion as all the values in the data set are considered. Therefore the researcher can get a more accurate representation of the dataset’s measure of dispersion compared to the range which only takes into account the smallest and largest value, so it can be skewed by extremely high or low values.
Why do psychologists use descriptive statistics?
-Psychologists use graphs and diagrams and charts to show data in visual displays because information provided in graphs and charts is easier to understand.
Describe histograms.
-Histograms show frequencies in columns.
-Histograms should be used to display data distributions of continuous data and there should be no gaps between the bars.
