psychology comp 1: standard deviation

standard deviation, graphs

what is standard deviation?

tells us how spread out the data is- it is a measure of how far each observed value is from the mean

what are the 5 steps when wanting to calculate standard deviation?

1) find the mean

2) take away the mean from each score

3) square each deviation to make them positive

4) add the squared deviations together

5) then square root

what is a normal distribution curve?

a symmetrical bell shaped probability distribution where the mean, median and mode are all equal- no skew

what closely follows a normal distribution curve?

heights of people, size of shoes, intelligence etc

what is a skewed distribution curve?

a non symmetrical graph that typically leans towards one side either left or right

what are the 3 percentages that match each standard deviation mean?

68% of values are within 1 standard deviation of the mean

95% of values are within 2 standard deviation of the mean

99.7% of values are within 3 standard deviation of the mean

where is the mode, median and mean on a graph?

mode- the peak of the graph

median- middle of the graph

mean- where the curve begins slope