Measures of central tendency & variability Flashcards
What is the MODE, how to find it/when to use it?
Measure of central tendency - the one that comes back the “most often” - create a frequency table to find it more easily. The mode is always used for categorical/nominal data.
What is the MEDIAN, when to use it/how
The median is our middle figure in the data, take each score of data and find the middle one, if two numbers in the middle, take these two numbers and do their average. Median is used for Ordinal data, and sometimes for interval/ratio, if data seem to have a skew or outliers
What is the MEAN and when to use it/how
Measure of central tendency, generally the one we use the most in psycho, suitable for continuous data level
How can you check which measure of central tendency to use?
Plot the data, if data is continuous, best to use a bar chart
How do you calculate the variance (average deviation of each score from the mean) ?
take each score and subtract from the mean, the result obtained is always equal to zero, however you can square each of the individual scores. Then, take the total of these, and divide it by number of data points (N for a population or N-1 for sample) to find the average/variance mean of our data.
Population variance formula in words
Sum of the squared deviations minus the population mean divided by the number of observations
Sample variance in words
Sum of square deviations minus the sample mean divided by the number of observations minus 1.
How do you calculate the Standard deviation and why
Bc the variance result is in a squared score, in order to come back to the original unit of measure, we square root the variance score.
What does the error bar represent in a bar chart graph representing our mean and SD
Error bar is used to show one standard deviation above and below the mean, for each of the “peaks”
