Flashcards in Statistics formula Deck (33):
What is the formula for standard deviation?
Sqrt(Sxx / n-1)
What is sxx?
(X1-meanx)^2 + (X2-meanx)^2+...+(Xn-meanx)^n
- Sigmax^2 - nxbarsqaured
What is variance?
S^2 so sxx/n-1
When do you use n and when do you use n-1?
1. For a full population, n
2. For a sample, n-1 (usually this)
How do you work out the probability of (AnB) if they are independent?
P(AnB) = P(A) x P(B)
Independent means with replacement
How do you work out the probability of (AnB) if they are mutually exclusive?
P(AnB) = 0
How do you work out (AuB) regardless if they are independent or mutually exclusive?
P(AuB) = P(A) + P(B) - P(AnB)
How do you work out P(AIB) always? And Independent? And mutually exclusive?
P(AIB)= P(AnB) / P(B)
If independent t it is just P(AIB) = P(A) since the P(B) cancels out
If mutually exclusive P(AIB) = O as you are dividing O by something
How do you always work out P(AnB)?
P(AnB) = P(BIA) x P(A)
What is the linear coding for Fahrenheit and Celsius?
F = 9/5C + 32
C = 5/9(F-32)
How do you calculate outliers?
-Data which is more than 1.5 x IQR
-Q1 - 1.5xIQR
-Q3 + 1.5xIQR
-mean - 2xsd
-mean + 2xsd
-If test scores, include all outliers (distribution continuous) except zeros where the candidates did not take the test)
-If not include say why bad experiment, taking a joke
How do you do quartile?
Look at notes
How do you work out mean?
How do you find IQR of even set of numbers?
-Split down middle
-Odd number on both sides
-Find middle position number of both
What is msd? (Mean squared deviation)
sxx / n
What is rmsd? (Root mean squared deviation)?
sqrt ( sxx / n )
What is the modal group? What is mode? What is bimodak?
-The range where the large promotion of the sample are in and it is the group with the most members
-The single value is called the mode
-If a second peak, even if one frequency is higher than the other
-Look at notes
What is the skew if the hump is closest to the y axis?
What is the distribution is the hump is further from the y axis?
What is frequency density?
frequency / class width
Which boundary do you plot of cumulative frequency?
When do you use a vertical line graph?
-Used to illustrate discrete data
-The scores can only take integer values
-Y axis is labelled frequency
How do you work out the median of any data?
The median Q2 is the value of the n+1 / 2 th item of data
What are the four measures of central tendency?
Mean, median, mode and midrange
If A and B are independent then P(BIA) is?
If A and B are dependant then P(BIA) is?
- not P(BIA’)
-P(BIA) = P(BnA) / P(A)
If A and B are dependent then what is P(AnB)?
P(A) x P(BIA)
If A and B are independent then what is P(AnB)?
P(A) x P(B)!
How do you work out P(B)?
P(B) = P(AnB) + P(A’nB)
How do you work out E(x)?
- r x P(x=r) all added
-also known as mu
How do you work out E(x^2) ?
How do you work out variance?
E(x^2) - mu^2