Parametric Tests Flashcards
what data can parametric tests test
continuous and discontinuous distributions
examples of continuous data
length, time, mass
what do parametric tests tell you
the probability of a value falling within a range
what is a normal distribution defined by
mean + varience
what is the variance
the standard deviation (from the mean)
what are meristic characters and examples
Countable structures that can’t come in halves eg bristles on a fly, chicks in next
when can you use parametric stats on meristic data
if their distribution is normal
What is the test for normality
Shapiro-Wilk test for normality
what is the null hyp in S-W
normality is the n0
What should you do when testing for normality if two data sets are being compared
both should be tested separately for normality
you do a shapiro-wilk test for normality and you get a significant result, what does this mean
you reject the null hypothesis - your data is NOT normal
what is the population distribution and what are paramiters
pop distribution is defined by parameters - you want to infer something about a population and you describe a population with parameters
what is the standard error of the mean
tells you how different the sample mean is from the population mean =
standard deviation/ square root of the sample no.
what is the central limit theorem
95% of observations will fall in the range of +- 1.96 standard deviations from the mean
why do smaller sample sizes need a bigger value than 1.96
to include 95% of the distribution
what test is done for small sample sizes
students t test
what does a students t test used for
comparing 2 small samples
what is the null hypothesis for the students t test
n0= the two samples were drawn from the same population
what is a t test used for and example
to compare means of two different samples from the same population eg. treatment and control
what is the analysis of variance/when is it used
ANOVA - more than 2 samples, range of samples with different treatments
You have a large variation in your sample, you want to work out what proportion of that variation is due to the differences between types of sample and proportion due to variation in each sample - what test
ANOVA - analysis of varience
What is the treatment effect
deviation from grand mean
What is the residual effect
deviation of individual from the mean for its group eg. genotype of a fly
