Statistics

Question 1

What is the measure of central tendency?

Answer 1

Spread / skew of data, measures location of middle / center of distribution

Mean, median, mode

Question 2

What is the standard deviation? normal distribution? frequency distribution?

Answer 2

+/- 1 standard deviation from the mean is 68% of the data
+/- 2 standard deviations from the mean is 95% of the data

Normal distribution: bell curve between -2 and +2 standard deviation

Frequency distribution: frequency of different outcomes / types

Question 3

What is a standard deviation test?

Answer 3

Determines if difference is likely / unlikely to be significant

Likely if difference between averages > greater standard deviation

Question 4

What is a t-test?

Answer 4

Whether difference between data sets is significant

Calculated t-value > critical value means it’s significant

Question 5

What is the p-value in biology?

Answer 5

p = 0.05 (5%)

5% probability differences are due to chance rather than real difference

Question 6

How are degrees of freedom calculated for t-tests?

Answer 6

df = (total of first data set, n’a + total of second data set, n’b) - 2

Question 7

What goes into a standard deviation conclusion?

Answer 7

Averages for each condition

Difference in averages, compare to standard deviations

Interpret if indicates likely significant difference

Report analysis in terms of focused question

Question 8

What goes into a t-test conclusion?

Answer 8

Averages for each condition

Report calculated value of t, critical value of t, degrees of freedom, p-value

Interpret if indicates significant difference

Report analysis in terms of focused question

Question 9

What is a chi-squared test?

Answer 9

Used to determine if hypothesis should be accepted / rejected
Erroneous decision > 5% of the time

Degrees of freedom is 1 less than number of phenotypes

Calculated value < table value to accept