Chi-Square Test of Association Flashcards
What is the probability of an event always between?
0 & 1
What does a p-value of 0 mean?
There’s no chance that the event will occur.
What does a p-value of 1 mean?
The event will always occur
What does P(E) = 0.5 mean?
The probability of event (E) is 0.5/ 50%.
Why do we use p-values (from a statistical test)?
To decide whether/ not to reject the null hypothesis.
What do p-values represent?
The theoretical probability of obtaining our data when the null hypothesis is correct.
What do inferential statistical tests spit out?
P-values (& other valuable information)
When do you use the Chi-Square Test of Association?
When testing for the presence of a relationship between 2 categorical variables & when you have a between-subjects (unrelated-subjects) design.
What type of test is the Chi-Square Test of Association?
An inferential test
When do you use the t-test?
When testing for a difference between the means of 2 numerical variables, when you have a between-subjects (unrelated-subjects) design, or a within-subjects (related-subjects) design
What type of test is the t-test?
An inferential test
What are 2 examples of experimental hypotheses (HE)?
“Medical outcomes differ by treatment centre” & “there’s a relationship between age & playing video games (N=100; 50 adults)”
What is an example of a null hypothesis (H0)?
Medical outcomes don’t differ by treatment centre.
How do we test that the results of a study are compatible with the null hypothesis being true?
By testing the probability that the results of the study are compatible with the null hypothesis being true
How do we come up with the theory behind a lab report?
By developing a novel hypothesis
How do we identify questions when planning a lab report?
By designing a study to test your hypothesis
How do we come up with the experimental design behind a lab report?
By applying for ethical approval.
How do we incorporate statistics into lab reports?
By performing a study, collecting data & analysing the data.
What needs to be presented & evaluated when we write lab reports?
Our findings
What do we need to have to perform a study & gather statistical data?
An IV & a DV
What is an example of an IV?
Type of university
What is an example of a DV?
Whether a group survives or dies.
How do we know the level of measurement of data sets?
By designing studies to test hypotheses, applying for ethical approval, then performing the studies & collecting & analysing the data.
In a study looking at whether type of hospital, out of 4 different types, affects survival rates, should the proportion of people surviving be similar or different across all 4 locations if the type of hospital makes no difference to the outcome?
Similar
In a study looking at whether type of hospital, out of 4 different types, affects survival rates, if all 4 treatment centres are drawn from the same population, are any differences we see due to chance or due to causation?
Due to chance
What are 2 examples of categorical data?
4 different types of treatment centres & whether patients die or survive.
When can we not compare mean differences between data sets?
When we have categorical data
What can we do when we can’t compare mean differences between data sets?
Compare portions & decide whether/ not the data collected is compatible with the null hypothesis being true
What is an example of a binary outcome?
Whether patients die or survive.
In a study looking at whether type of hospital, out of 4 different types, affects survival rates, what do we do as we can’t compare mean differences between the data sets as each data set contains categorical data?
Compare portions & decide whether/ not the data collected is compatible with the null hypothesis being true (i.e., that there’s no systematic difference in survival rates across hospitals).
How can we calculate the probability of observing the pattern of results obtained if the null hypothesis is true?
Using inferential statistics
How do we decide whether/ not the data collected from 2 or more portions is compatible with the null hypothesis being true?
By using p-values
When do we reject the null hypothesis?
If the probability of there being a difference between observed values (results obtained) & what we would expect by chance (if the null hypothesis were true and there is no relationship between sets of data) is low (the p-value is small).
When do we decide that it’s unlikely that we would’ve observed a pattern of results by chance alone?
If the probability of there being a difference between observed values (results obtained) & what we would expect by chance (if the null hypothesis were true and there is no relationship between sets of data) is low (the p-value is small).