Statistics Flashcards
What is the purpose of the students T-test?
To find out if the difference between means is significant.
When is the value significant for a t-test?
If the value of t is GREATER THAN or EQUAL to the critical value, the difference between the two means is significant and you can REJECT the null hypothesis.
If I want to know if the difference between 2 means is significant what statistical test should I use?
T - test
If the value of t is GREATER THAN or EQUAL to the critical value, the difference between the two means is significant and you can REJECT the null hypothesis.
What is a null hypothesis?
A statement that says that there will be no significant difference / correlation between the things you are measuring. Purpose of statistical tests is to disprove the null hypothesis.
Define standard deviation.
Standard deviation shows the ‘spread of data around the mean’
Is it better to use standard deviation or range to evaluate data?
Standard deviation because SD is less affected by anomalous results
From standard deviation values you can plot error bars on a graph. If error bars overlap, what does this mean?
There is no significant difference between data values.
What does the Hardy-Weinberg principle predict?
It predicts that the frequencies of alleles in a population wont change from one generation to the next, but is only true under certain conditions.
What are the assumptions of the Hardy-Weinburg principle?
Assumptions:
Population must be large
There must be random mating/fertilisation
No migration
No mutation
No selection pressures ( no allele must be favourable/more beneficial
What is the purpose of the Chi-squared test.
Purpose: If you wanted to compare observed vs expected frequencies
Is there a difference between the frequency of different bird species at 2 different sites?
What statistical test should I use
Chi-squared
because you are comparing frequencies between groups
When is the value for Chi-Squared significant?
If your value for Chi-Squared is EQUAL TO or GREATER THAN the critical value, there is a significant difference between expected and observed and you can REJECT the null hypothesis.
If the standard deviation is small what does that tell us about the data?
The data is more consistent
When would I use Spearman’s Rank Correlation Coefficient?
To test for correlation between two variables
What does Spearman’s Rank Correlation Coefficient tell you?
It shows strength and direction of a correlation (from -1 to +1)
Use critical value table
IF calculated value GREATER or EQUAL TO the critical value then we can REJECT the null hypothesis there is a significant correlation.
What does standard error show?
Shows how accurate the mean is
If the Probability (p) value is less than 0.05 what does this mean?
The data is significant
There is less than 5% chance that the difference is due to chance
reject the null hypothesis
