Warm-up Wednesday, 1-21-15

You are a scientist and you finished your experiment. What do you do with your data? Discuss with your group members and we will talk as a class.

Homework

1. Chapter 16 outline due Monday, January 26th

2. Bring your lab notebooks tomorrow, along with the lab rubric.

3. Print out the lab worksheet packet tonight and bring it tomorrow.

You analyze it!

You can describe it by calculating descriptive statistics.

You can also analyze it for significance

Mean

Mean = Average = Sum of values sample size

Standard deviation• A statistic that measures the amount of deviation of data fromthe mean.

Descriptive statistics: Mean and standard deviation

Statistical analyses

All statistical tests do the same general thing: use your data to calculate a statistical value. Using that statistical value and your sample size, you calculate a p value, where p stands for probability.

In statistics, when p < 0.05, this means that your independent variables (treatments) do have significant effects on your dependent variables.

Chi-square test

• A test to see if there is a difference between the expected and observed frequencies.

• Frequency here means values, usually count data (that is data that you can count as 1, 2, 3, etc.)

Hypotheses in statistics

Null hypothesis: a hypothesis in which the independent variables don’t affect the dependent variables.

Hypothesis: the independent variables do affect the dependent variables

Chi-square

Key points of chi-square

1. The expected values between your treatment groups are always equal

2. The observed values for each treatment group come from your actual data

3. You will need to know your sample size and use this to calculate your degrees of freedom

4. You will then calculate your p-value based on your calculated chi-square and degrees of freedom values

What to do with descriptive statistics