Biostats Exam 3 (Comparing Means)

t-test

evaluate the size and significance of the difference between two means

One-sample t-Test

When you want to compare a sample mean to some known or hypothesized value

Independent samples t-Test

compare two groups to one another

Repeated Measures t-Test

How a group changes over time

One sample t-test data

interval or ratio data

What is unknown in a One sample t-test

The true standard error of the mean

Degrees of freedom in a one-sample t-test.

n -1

one-sample t-test statistics (t)

test statistic

one-sample t-test statistics (df)

degrees of freedom

one-sample t-test statistics (sig)

p value for the test statistic

Independent Samples t-test data

interval or ratio data

What makes a Independent Samples t-test different from one another

The samples are independent from one another

Independent Samples t-test Degrees of freedom

n-2

Test Variables

the variables you want to investigate

Grouping Variable

the variable that will split your data into two groups

Paired Samples t-Test data

interval or ratio data

Paired Samples t-Test measures

two variables with values paired by subject

Paired Samples t-Test Degrees of freedom

(n / 2) -1

Reporting Pearson correlation

r(N) = .sig, p =

Nonparametric tests

No need for normality

Nonparametric tests data

ranked/ordinal data

The 1-Sample Kolmogorov

Smirnov is used to test normality of data

Independent Samples will produce

Mann-Whitney U

Related Samples will let you calculate

Wilcoxon Rank-Sum

Exact significance

the exact significance is calculated from all potential distributions

Asymptotic significance

calculated using an estimated curve

Monte-Carlo significance

uses a random process to estimate the significance using areas under the curve

One Sample T

comparing a sample to a hypothesized mean

Independent Samples T

comparing two groups on some value

Repeated Measures T

comparing two variables within a set of subjects

Parametric or Nonparametric?

Parametric because they are more statistically powerful