Bio Stats

Question 1

What does small vs large SD represents

Answer 1

Small- means more tightly clustered around mean ,less variation, more reliable results
Larger -more variation less tightly clustered around mean

Question 2

What are t-tests for and when would we use t -tests

Answer 2

Compares the means of 2 groups and determains if any of the observed differences are due to chance of if they are significant statistically
Used when- comparing 2 sets of data
Data is continuous (can take any value across a range e.g height of plants so not categoric like blood types e.g)
-sample size is small

Question 3

What is H0 for t tests, spearman’s rank and chi squared

Answer 3

-no sig between 2 sets of data given

Question 4

How do i prove that the null hypothesis (that there is no sig between to sets of data) is wrong in t tests

Answer 4

Calculate t use formula -will always be postive even if we get - turn to +
Calculate DF (sample size in group one +sample size group 2 -2)
Go to t-test table , go to where p=0.05 ( find intersection of DF and 0.05 )
-if ur t value is greater than this value
Null can be rejected
Since p<0.05

Question 5

What is chi squared test for when is it used ,what do results show us,degree of freedom

Answer 5

To test the significance between observed and expected frequencies of normal data
-sample size big
-data is categoric
Results show us -if dif between expected and observed are significant or so small can be neglected
Degree of freedom -number of categories -1

Question 6

How do i show dif between O and E value is significant

Answer 6

Calculate x2
Then calculate DF- categories-1
Intersection of p=0.05 and degree of freedom
If ur calculated x squared value is higher than the intersection
H0 rejected ,data is significant
As p<0.05

Question 7

What is spearman’s rank for

Answer 7

Measures monotonic relationships that are not linear
Assessing data points that are independent of each other
Null- no correlation between a and b
Assign ranks from highest to lowest value for both variables and find dif between ranks
If u get same score for variable then u you add the ranks and average, e.g if variable 35 ties for 3rd place and fourth place u add and divide by 2 to findings rank
Calculate rs
The find intersection of sample size and p=0.05
If rs is greater than this intersection h0 is rejected
And we can show weather its negative correlation (closer to -1) or positive (closer to 1)