Single Factor Research

dataCentral tendency variablitycorrelation Nominal moderangephi Ordinal medianrangeSpearman rho Interval/ Ratio Skewed medianrangeConvert to ranks Spearman’s rho Interval/ratio meanStandard deviation Pearson r regression

Type of designParametricNon parametric One sample Population sd known Z testnone One Sample Population sd unknown One sample t-testnone Two independent samplesIndependent t testMann-Whitney U Rank sums test, one way chi-square Two related samplesRelated (paired t test)Wilcoxon test Three or more independent samples (1 factor) Between subjects ANOVA Post hoc test – HSD or protected t Kruskal Wallis H Or one way chi squared Post hoc test Rank sums test Three of more related samples ( 1 factor)Within subjects ANOVA Post hoc test – HSD or protected t Friedman Post hoc Nemenyi’s test

If I want to test the efficacy of a new drug on blood pressure then I have some choices of design….

Two independent samples Control vs drug groups (random assignment) Comparison is independent t- test Or Mann -Whitney U

Non-equivalent groups Eg Sick vs Healthy Male vs female…. Comparison is independent t- test Or Mann -Whitney U

Matched design. Pairs of twins sign up for study One twin is in control group the other in drug group Comparison is paired t-test Or Wilcoxon

Repeated design Take a baseline measure of BP for each subject Then give drug Repeated (paired) t-test Wilcoxon

CONTROL GROUPS – provide baseline for comparison

No treatment Compare treatment vs no treatment (no treatment only difference is variable of interest) Standard control for : Situational Task or Instructional difference

Placebo Standard for drug trials Or obvious clinical treatments Inert substance given for comparison Tests the protocol Tests the beliefs of treatment

Waiting List If no treatment or placebo are unethical or not possible then assign subjects to waiting list. Must be done randomly (not first come first serve)

Yoked Executive Monkey Experiment Two monkeys ‘yoked’ together Executive controls off switch the other is helpless Both get shocked equally

No treatment PlaceboWaiting ListYoked Perception of Treatment noneBelieve treated Believe will be none Beliefs effect Beliefs irrelevant Beliefs relevant Beliefs Relevant Beliefs Irrelevant No treatment baseline yesnoyes IV - control yes Different amount of IV possible

Only two levels Advantage Simple Direction of difference obvious Disadvantage Deceptive appearance of linearity Single hypothesis test