IB Biology HL Topic 1: Statistical Analysis

What are error bars?

Graphical representations of the variability of data

Give the equation for the mean of a set of data.

Mean=sum of all samples/sample size

What does the standard deviation do?

Summarizes the spread of values around the mean.

68% of the values of a set of data fall within ........... of the mean

+/- 1 standard deviation

What kind of distribution can a standard deviation be applied to?

Normal distribution

When is a standard deviation considered to be small?

When it is less than 33% of the mean

When can a student T-test be used?

When the data is unmatched, at the interval level, has a minimum sample size of 10 for each data set, has a normal distribution and has similar variances

What is the student T-test used for?

Distinguishing marginal differences between sets of data

Give the 3 steps of the student T-test.

1) Calculate the degrees of freedom 2) Find the critical value for t 3) Determine the significance

How do you calculate the degrees of freedom for a student T-test?

Add the number of values in each data set together and subtract 2.

How do you find the critical value for t?

Look at the table of critical values along the row for the degrees of freedom and find the value corresponding to a probability value of 0.05

How do you determine the significance for T?

If calculated value>critical value, a significant difference exists.

Does a positive or negative correlation between 2 variables imply a causal relationship?

No.