Methodology: Stats Flashcards
What are descriptive statistics?
Ways of summarising data from research.
Give an example of a descriptive statistic.
A graph such as a bar chart or frequency distribution.
What are the measures of central tendency?
- Mean
- Median
- Mode
Define ‘mean’.
The average result from a number of scores.
How is a mean calculated?
Adding data together and dividing by the number of scores there are.
Define ‘median’.
The number in the middle of a data set with as many scores above as it has below.
How is a median calculated?
By listing values in a data set in order of size and finding the middle.
What do you do if there are two medians?
Calculating the mean of the two central numbers by adding them together and dividing by 2.
Define ‘mode’.
The most frequently occurring piece of data.
What names are given when data has 2, 3, or 4 modes.
2 - bimodal
3 - trimodal
4 - multimodal
How is a mode calculated?
Looking for the most frequently appearing value in a data set.
How might a mean calculate a misleading figure?
There may be few extremes or an anomaly in the data that would skew the mean.
What are the measures of dispersion?
- Range
- Standard deviation
Define ‘range’.
The difference between the largest and smallest value in a data set.
How is a range calculated?
By taking the smallest number away from the largest.
Define ‘standard deviation’.
The average distance between values of a data set around a mean.
What does a large standard deviation indicate?
That the scores are widely dispersed in relation to the mean.
What does a small standard deviation indicate?
That the scores are closer to the mean.
Identify the 6 steps to working out standard deviation.
1) Find the mean of a data set
2) Minus the mean from each value in the data
3) Square each new value
4) Add all the squared values together
5) Divide the total by number of scores -1
6) Square root that value
Define ‘frequency’.
The number of times a particular event or piece of data occurred.
How are frequencies displayed?
On a frequency distribution curve.
Describe the shape of a normal distribution.
A bell curve.
What are the two types of descriptive statistical data that can be found in a frequency distribution?
- Central tendencies
- Measures of dispersion
Describe the features of a normal distribution of central tendencies.
- The mean, median, and mode all occur at the same point with the same value
- It has the same shape either side of the mean as the pattern of values is exactly the same above and below the median
Describe the features of a normal distribution of measures of dispersion.
- Knowing the mean and the standard deviation of scores on a normal distribution allow us to work out what scores fall within certain limits
- The proportion of scores falling above or below the mean (the centre) by 1 standard deviation is 34%
- The proportion of scores falling above or below the mean (the centre) between 1 and 2 standard deviations is 13.6%
- The proportion of scores falling above or below the mean (the centre) by 2 standard deviations is 2.4%
What are the two alternatives to a normal distribution?
- Positive skew
- Negative skew
Describe the features of a positive skew distribution.
- The mode is the highest point, then the media, then the mean and gets small the higher it is on the Y axis and lower on the X axis
- It is due to extremely high scores that affect the mean
Describe the features of a positive skew distribution.
- The mode is the highest point, then the media, then the mean and gets small the higher it is on the X axis and lower on the Y axis
- It is due to extremely low scores that affect the mean
What does a skewed distribution show?
That there is a large spread of data due to an anomaly.
List the 4 types of hypothesis tests.
1) Wilcoxen Signed Ranks Test
2) Mann Whitney U Test
3) Chi-Squared Test
4) Spearman’s Rho Correlation
Define ‘nominal data’.
Categories that are not measured or ordered.
Define ‘ordinal data’.
Values that have ranks.
Define ‘interval/ratio data’.
Measuring the distance between attributes/there is always an absolute zero.
Why are inferential statistics used?
To determine the significance of data or whether it was simply due to chance.
What level of significance do Psychologists use?
0.05, a 95% chance that results aren’t due to chance.
Describe the conditions for which to use a Wilcoxen Signed Ranks Test.
- Testing a difference
- Repeated measures
- Ordinal data
Describe the conditions for which to use a Mann Whitney U Test.
- Testing a difference
- Independent measures
- Ordinal data
Describe the conditions for which to use a Chi-Squared Test.
- Testing a difference
- Independent measures
- Nominal data
Describe the conditions for which to use a Spearman’s Rho Correlation.
- Testing a relationship
- Ordinal/interval data
