# Data Lecture 5-6. Part 1

version from 2017-10-16 09:56

## Section 1

What are the 3 types of T test One sample t-test, two-sample t-test, paired t-test.
One sample t-testwhich is used to compare a single mean to a fixed number or “gold standard” – We covered this in first year. How many standard deviations is the mean of the sample away from the population mean value.
two sample t-testis used to compare two population means based on independent (unpaired) samples from the two populations or groups
paired t-testis used to compare two means based on samples that are paired/repeated measures (dependant) in some way
When is t-test not approproatewhen you are trying to compare more than 2 groups /samples.
What is the purpose of the one sample t-testThe main purpose is to see whether there is evidence that the population mean from the sample is different to the specified value. Related to the one-sample t-test is a confidence interval on the mean. Calculates how many standard errors the sample mean is away from the expected value. The further away the mean is from the expected value, the larger the value of t, and the less probable it is that the real population mean could be the expected value.
equation for one sample t-testsample mean- population mean / standard error
What parametric assumptions does the one sample t-test need to meet -continuous ratio/interval data. -data that are drawn from a population that is normally distributed (test with skewness and kurtosis statistics or any statistic that tests for a normally shaped distribution).
what assumption do you also have to check for independent t tests The samples being compared come from populations that have the same variance