selecting and using statistical tests Flashcards
what does standard deviation look like on a calculator?
s2x
How do you plot error bars?
plot highest and lowest value
what does a smaller error bar mean?
low spread, data is clumped around the mean, more reliable
what does a larger error bar mean?
larger spread, less reliable
What does it mean if error bars overlap?
There is no significant difference between the two sets of data, due to chance.
what test do you use if you are finding the number of individuals in particular categories?
X2 test
What test do you use for looking for differences between mean values?
students t test
What test do you use for looking for associations between different measurements from the same sample?
spearman rank correlation
what is equation for chi-squared test?
x2 = (O-E)2/ E
add up all results and that gives x2
where O is results observed and E is expected
what is the null hypothesis for the chi-squared test?
there is no significant difference between observed and expected frequencies
How do you find the degrees of freedom?
number of categories-1
What is the interpretation of the data if the value is bigger than the degree of freedom for chi-squared test?
there is less than 5% chance that the differences are due to chance. we must reject null hypothesis
What is the equation for spearman’s rank test?
1-( 6x d2/n3 - n)
where d is the difference between each pair of measurements and n is number of pairs of items in the sample
What is the null hypothesis for the spearman’s rank test
There is no correlation between (variable 1) and (variable 2)
What is the interpretation of the data if the value is bigger than the degree of freedom for the spearman’s rank test?
There is less than 5% probability that the positive correlation between the (variable 1) and (variable 2) is due to chance. we reject null hypothesis.
