BIO 225: Types of Data and when to use them

When to use what and with which types of data

Independent Sample T-test

used when you want to determine whether there is a statistically significant difference between the means of two separate, unrelated groups

Stratified Random Sampling

Used when trying to evaluate data from different subgroups or strata; when researchers are aware of subdivision within a population that need to be accounted for

P-value

the probability that the observed difference in the means of our two groups is due to random chance, expressed as a decimal between 0 and 1 (0% and 100%)

Null Hypothesis Rejection

When p ≤ 0.05

Disadvantage of Stratified Random Sampling

the resulting sample may not be representative of the full population

Advantage of Stratified Random Sampling

removes variation and the chances of overlap between each stratum.

Simple Random Sampling

selects a smaller group (the sample) from a larger group of the total number of participants (the population)

Factors controlling herbivores

individual plant chemistry – food quality, defensive chemicals and where defensive chemicals are concentrated

Two Sample T-Test

used when comparing the means of two samples; used when we have a categorical (qualitative) independent variable with 2 possible values and a numerical (discrete or continuous) dependent variable

Interval Plot

used to assess and compare the means and confidence intervals; useful for comparing groups

The difference is not significant

What is determined when the interval bars of an interval plot easily over the mean of each group

Difference is Significant

What is determined when the interval bars of an interval plot do not overlap the mean of each group

Interval Bar

a vertical line with horizontal lines at the endpoints of the 95% confidence interval for the mean

Standard Error Bar

a vertical line with horizontal lines at one standard error (or multiple of the standard error) from the mean

Box Plot

used to assess and compare sample distributions

Information Yield of a Box Plot

minimum value, first quartile, median, third quartile and maximum of a data set

Histogram

a chart that plots the distribution of a numeric variable’s values as a series of bars. Each bar typically covers a range of numeric values called a bin or class; a bar’s height indicates the frequency of data points with a value within the corresponding bin.

Histogram Requirement

a variable that takes continuous numeric values

Bar chart requirement

A variable that is discrete or categorical

Bar Chart Design Feature

bars have a small gap between each other emphasizing the discrete nature of the variable being plotted

Line chart

Used when you have binned numeric data but want the vertical axis of your plot to convey something other than frequency information

Frequency Polygon

When a line chart is used to depict frequency distributions like a histogram

Density Curve

an alternative to the histogram that gives each data point a continuous contribution to the distribution

Accuracy

refers to how close you come to the right answer

Precision

refers to how close each of your measurements are together

Confidence Limits

tell us how precise our estimates are