Maths for biology

I used these videos to create: https://www.youtube.com/watch?v=op3GPJYpcvk&list=PLOfYYgIrtVMgVDUYVjwoBKiN1PkInY9hL

What does Standard Deviation mean?

The measure of how spread out all the repeats are from the mean.

What is the advantage of using Standard Deviation instead of the range?

• SD shows the spread of data around the mean, whereas the range is only the difference between the highest and lowest value.

• SD reduces the effect of anomalies, where as the range includes anomalies.

• SD can be used to indicate whether a difference between the results is significant.

Why would knowing the standard deviation be more useful for a conclusion?

• If there is no overlap between the groups, likely there indicates significant difference

• If there is an overlap between the groups, this likely indicates there is no significant difference.

How can you determine Spearman’s test is used?

• To investigate if there is a correlation between two variables.

  • If the data includes continuous data (taking measurements)

  • Investigating an association between two measurements

Null Hypothesis test for speakerman’’s test:

There will be no significant correlation between (variable 1) and (variable 2)

Conclusion based on P valve and significance (0.05 and n = number of samples)

• If r_s = 0.616 and P-value = 0.6786

• So we accept null hypothesis, so suggests there is no significant correlation

• If r_s = 0.7 and P-valve = 0.6786

• So we do not accept null hypothesis, so suggests there is a significant correlation

How can you determine Student T test is used?

• To test to see if there is a significant difference between mean of values.

  • Contains continuous data (taking measurements)

  • Investigating a difference between two means

Null hypothesis for student T-test:

There is no significant difference between the two means of (variable 1) and (variable 2).

Conclusion for Student T-test:

If calculated value is greater than degree of freedom:

• We reject null hypothesis as the calculated value is more than critical value

• There is less than 5% probability that the difference is due to chance

If calculated value is smaller than degree of freedom:

• Accept null hypothesis as the calculated value is less than critical value

• There is more than 5% probability that the difference is due to change

How can you determine Chi squared test is used?

• Used to test between the expected value and actual value

  • Frequencies, counting how many individuals are in a category

  • Investigate a difference

Null hypothesis for Chi squared test:

There will be no significant difference between the observed (X) and the expected (X) for (variable 1) and (variable 2).

How is degrees of freedom calculated?

• Df = n - 1

• Where n is the sample number

Why do we use log scales?

Used to help compare values that have a large range (comparing very small values to very large values). [log₁₀ => y-axis]

Converting to log and back:

If log₁₀X = 7.55

10^7.55 = X