Y2 Stats Flashcards
What does the PMCC describe?
The linear correlation between 2 variables, from -1 to 1.
What does y = ax^n equal in log form?
log y = log a + n log x
What does y = kb^x equal in log form?
log y = log k + x log b
What do you do for exponential modelling questions?
Sub between x / y and whatever they’re coded to as needed
What is PMCC represented by?
Letter r for a set of data
What does PMCC +- 1 represent?
All the points lying on a straight line
What does A U B mean?
Event A or event B. So union of them.
What does A intersection B represent?
A and B, overlap of them/
What does P(A|B) mean?
Probability of A happening given that B has already occurred.
What happens if P(A|B) = P(A)?
Then events A and B are independent.
How much data is within 1 standard deviation of the mean for a normal dist?
68%
How much data is within 2 standard deviations of the mean for a normal dist?
95%
How much data is within 3 standard deviations of the mean for a normal dist?
Around 99.7%
What does the standard normal dist. have?
Mean 0, standard deviation 1.
What is the standard normal dist. written as?
Z ~ N(0,1^2)
How do you code normal distributions to the standard normal dist?
In form X ~ N(u, var^2)
Z = (X - u) / var.
Allows you to find amount of standard deviations away from the mean. Could also just use InvN.
How do you approximate a binomial dist to a normal one?
u = np (duh)
var = root(np(1-p))
How do continuity corrections work?
You should only include values that will ROUND to the binomial’s bound. Pay attention to less than or less than / equal to.
What is the sample mean for a sample size n distributed along X ~ N(u, var^2)?
Xbar ~ N(u, (var^2)/n). So just divide var^2 by n.
How do you standardise the coding to a sample mean? So coding
Xbar ~ N(u, var^2/n).
Z = (Xbar - u) / (var/root(n))
