4.3.7 applying statistical techniques
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correlation coefficient
measure of how closely 2 sets of data are correlated - value of 1 means perfect correlation
standard deviation
measure of spread around mean
students t-test
test used to compare 2 means
what does a low standard deviation imply
data has a narrow range & the points are closely grouped to the mean - could indicate greater reliability
what does a high standard deviation imply
data points have a larger range & are less well grouped - may indicate lower reliability
formula for standard deviation
pg 290 in textbook
what do these symbols mean in the standard deviation equation s x x̄ n
s = standard deviation x = individual value x̄ = mean value n = number of data points
first thing when conducting a student’s t-test
state a null hypothesis that there’s no significant difference between the means of these 2 sets of data –> the student’s t-test measures whether we can reject/must accept it
formula for students t-test & meaning of each symbol
pg. 290 of textbook
degrees of freedom
defined as number of values in a statistical calculation which are free to vary
what do we use the result of the student’s t-test for
compare the degrees of freedom to table of t-values
formula used to calculate correlation coefficient
spearman’s rank correlation
formula for spearman’s rank correlation & meaning of each symbol
pg 291 of textbook
what must we state for spearman’s rank correlation
null hypothesis
what table do we use to assess whether the value of Rs indicates a correlation
table of critical values