15: Statistical tests

Question 1

What is standard deviation?

Answer 1

a measure that is used to quantify the amount of variation or dispersion of a set of data values. A low standard deviation indicates that the data points tend to be close to the mean of the set, while a high standard deviation indicates that the data points are spread out

Question 2

How do you calculate standard deviation?

Answer 2

1) Find the mean of the data set
2) Subtract the mean from each number to find the deviation from the mean
3) square the result and total that column and you have the top of the equation E(x - X)2
(that means the sum of the number minus the mean squared)

Question 3

When do you use spearemans rank?

Answer 3

When you are compring the relationship between two variables

Question 4

What statistical test would you use to find out if the mean mass of lobsters is high in areas where collection is banned?

Answer 4

T-Test

This is because you are comparing two means, and these means are measured.

Question 5

What statistical test would you use if you needed to find out if fewer cars use a road when charging is introduced?

Answer 5

Mann whitney U test

This is because you are comparing two means, but you have counted the data.

Question 6

What statistical test would you use if you needed to see if crop yeild increases as fertiliser application increases.

Answer 6

Spearemans rank

This is because you are comparing the relationship between two variables.

Question 7

What statistical test would you use if you wanted to see if a new range of GM wheat produces more seeds than the traditional variety?

Answer 7

Chi squared

This is because you are comparing to frequencies (number of seeds)

Question 8

Do you accept or reject the null hypothesis if if the spearemans rank is smaller than the p-value?

Answer 8

You can accept the null hypothesis.

Question 9

When do you use the mann whitney-u test?

Answer 9

For when you compare two means and the data is either calculated or counted.

It test the overlap to see if the difference is significant enough for the factor to be the cause of change.

Question 10

What does R stand for in the mann whitney u-test?

Answer 10

The rank.

In this test you minus the sum of the ranks that are for that data set. (e.g. if it contained the ranks 2,4,5 and 6.5 then ER would be 17.5)

Question 11

When do you use a t-test?

Answer 11

When you are comparing the relationship between two means, but the data is measured.

Question 12

For chi-squared and the t-test, do accept or reject the null hypothesis if the value is bigger than the critical value?

Answer 12

You can reject the null hypothesis.