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z test

Independent samples t-test

1) Draw graph (p value > z crit)

Assumptions: 2 groups are independent

Nominal: Category; Ordinal: Not equal

2) Variance > S.D. > Standard error

and randomly sampled; DV measured on

diff. Eg. Level of closeness; Interval:

3) z formula

(at least) an interval scale; DV is normally

Equal diff.; Ratio: Absolute zero

Confidence Intervals

distributed; Equal variance in 2 groups

PSYC2012 Exam Formula Sheet

* Two-tailed crit value Point estimate:

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Interval estimate:

External validity: Can generalise the

Around mean diff.: Incl. 0 = Retain H0

results from sample to population?

Around mean: Incl. μ = Retain H0

Internal validity: Single explanation for

Cohen’s d

the relationship between two variables?

where Reversed form:

-

0.2 Small; 0.5 Medium; 0.8 Large

Reversal:

One sample / Related samples t-test

(Purchase note to view more!) df = N – 2 Unimodal & symmetric: All same

Cls: Constructed around μ1-μ2

Symmetric: Same mean & median Chi-square (X2) Goodness of Fit

Tightly clustered around μ = less variance Mean: ∑ (Value x Freq) / ∑ Freq; Median: Located at (∑ Freq + 1) / 2

df = k (categories) – 1 = 2

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Chi-square (X2) Test of Independence

Level of significance α = Type I error rate

β = Type II error rate

Two-tailed: df = (R - 1) × (C - 1) = (2 - 1) × (3 - 1) = 2

Higher power: Larger sample size / Smaller variance / Larger alpha / Onetailed test / Larger effect size

*If z-test, p=0.025 in each tail