stats Flashcards
what is the chi squared equation?
x squared= sum of (O-E) squared divided by E
how do you find degrees of freedom for chi squared?
number of classes -1
how do you know if your data sets have a significant difference using chi squared?
at the correct degree of freedom and 0.05 significant level, pick the value. If your worked out value is greater than the critical value than there is a significant difference between the data sets and the null is rejected
what does chi-squared work out?
If there is a significant difference between the expected and observed result
define valid
results that answer the original question- controlled all the variables
define accurate
results very close to true answer
define reliable
repeatable and reproducible- results will be the same
define precise
results don’t vary much from the mean
what are the 5 things to consider when asked to evaluate a study?
sample size (the greater, the more reliable), variables (the more variables that have been controlled, the more valid), data collection (should be unbiased), controls (increases validity), repetition (if other scientists produce the same results they are more reliable)
why use spearman’s rank?
to see is there is a significant difference between two variables- correlation or causation
when ranking data sets, what happens if there are 3 of the same number?
add what ranks they would be and divide by 3, give them all that rank
in spearman’s rank, when can the null hypothesis be rejected?
if your value is higher than the critical value
how do you find the critical value in spearman’s rank?
find the 0.05 significant level and find n (number of pieces of data, in one set not both)
what does a negative number in spearman’s rank mean?
a negative correlation
when comparing your worked out value critical value does it matter if the number is negative?
no- ignore sign when deciding wether to accept or reject the null
