psyc312-9

X = µ + (zσ)

• subjective (personal judgement)
• Analytic/Theoretical - study all possible outcomes
• Expected relative frequency (Empirical) - on the long run, average

• given mutually exclusive events, sum the probabilities
• keyword: OR

• for joint probabilities
• keyword: AND

• Used to test frequency distributions for ONE dimension
• E_i= np_i || df = (k-1)
• 

• E_r,c = (sum of Row) x (sum of column)
• sample size

df = (r-1)(c-1)

x²(observed) > x²(critical), reject the null

Random variability btwn observations or statistics due to chance

The distribution of a statistic over repeated sampling from a specified population

• the mean of the sample is equal to the population mean (no calculation)
• the standard deviation of the sample is (standard error of the mean)
• 

• The hypothesis that the manipulation had no effect.
• always contains = or ≤ or ≥

always contains ≠, < or >

• represent the point at which we reject the null
• we reject the null when we exceed the critical value

One tailed: one direction for rejection; left or right tailed

2 tailed: rejects null when value is too extreme in either direction; non directional

If p ≤ α (in critical region), reject the null

If p ≥ α (not in critical region), fail to reject the null

Type I error occurs if the null hypothesis is rejected but it's actually true (most serious)

Type II error occurs when the null hypothesis is not rejected but it's actually false