How to Do a Chi Square Test for AP Biology

Null Hypothesis

Null Hypothesis

Predicts no effect of the independent variable on the dependent variable.

Alternative Hypothesis

Predicts an effect of the independent variable on the dependent variable.

Chi Square

The value calculated in the statistical test to determine the significance of observed versus expected data.

Observed

The quantitative data collected during the experiment.

Expected

The values predicted before conducting the experiment, assuming no effect of the independent variable.

Degrees of Freedom

Used to determine the threshold value for comparing observed and expected data.

Statistical Significance

A determination of whether the observed data significantly differ from the expected data.

Critical Value

The value from a chi-square table used to assess whether to accept or reject the null hypothesis.

Application of Chi Square Test

Involves calculating χ² to evaluate hypotheses based on experimental data.

Coin Flipping Experiment

An example illustrating the application of the Chi Square test with expected results of a 1:1 ratio.

Hypothesis Testing

A method to make inferences or draw conclusions about a population based on sample data.

Null Hypothesis Acceptance

Occurs when observed data does not show significant differences from expected values.

Chi Square Equation

Used for comparing observed and expected frequencies to determine if there's a significant difference.

Summation Symbol

Indicates the total sum of the values in a statistical calculation.

Statistical Analysis

The process of collecting and analyzing data to identify patterns or trends.

Hypothesis Framework

Structure for testing statements about relationships between variables.

Alpha Level

The threshold probability used to determine significance, often set at 0.05.

Ripe Banana Experiment

A study that assesses spatial distribution preference of flies using a chi-square test.

Coin Flip Null Hypothesis

Indicates a prediction that a coin lands on heads 50% of the time and tails 50%.

Experimental Data

Data collected from observations or experiments that is used for analysis.

Coin Flip Alternative Hypothesis

Suggests deviations from a 1:1 heads to tails ratio.

Expected Frequency Calculation

Used to determine what the results would be if the null hypothesis were true.

Effect of Independent Variable

The influence that changes in one variable have on another variable.

Statistical Table Reference

A resource with critical values for determining significance based on degrees of freedom.

Observed vs. Expected Comparison

The central method in determining whether data supports or rejects hypotheses.

Chi Square Conclusion

The outcome of the chi-square test which indicates whether to reject or accept the null hypothesis.

Systematic Approach

A step-by-step method for solving chi-square problems.

Data Significance

Indicates whether the results of an experiment are meaningful or due to chance.

Coin Flip Data Calculation

The method of comparing observed results against expected outcomes in a coin flip experiment.

Behavioural Influence

In the fruit-fly experiment, refers to how the presence of bananas affects fly distribution.

Significant Difference Determination

Deciding if the difference between observed results and expected values is meaningful.

Chi Square Value Interpretation

Analyzing calculated chi-square values in context with critical values to draw conclusions.