when do you use chi-squared
used when looking at differences between frequencies (data that is counted) in different categories (known as discrete data).
when do you use students t-test
used to look at differences between means (averages) of data involving measurements (like lengths, or times).
when do you use spearman’s rank
used to look at the correlation between two variables in measured data.
when do you use standard deviation
measure of the spread of scores within a set of data
what is the chi-squared equation
X² = ∑(O-E)² / E
o = observed values
e = expected values
how can you calculate t-test
rank samples: 132
1. 1 2. 2 3. 3
in the next 2 columns, put your values in, eg score 1 and score 2
then u take away each value from score 2 from their corresponding score 1 value
X-Y X-Y²
1 3 = -2 4
2 6 = -4 16
3 2 =1 1
total values from X-Y and then X-Y²
input into equation
t = ((∑D/N) / -5/3
√ (D² - ((∑D)²/N) √(-5² - ((-5²/3)
(N-1) (N) (-5- -4) x (-5)
what is the spearmans rank equation
rs = 1 - (6∑di²) / (n(n² - 1))
rs = Spearman rank correlation coefficient.
di = difference between the ranks of each pair of values.
n = number of observations
