Statistics + Probability (topic 4)

Question 1

Mean

Answer 1

Average: add up all values, divide by the number of terms.

Question 2

Median

Answer 2

Middle value in an ordered data set. **Need to be in order first.

Question 3

Mode

Answer 3

Most common number in the set.

Question 4

Percentile

Answer 4

X percent of the data is below this.

Question 5

Quartile

Answer 5

Q1 = first quartile = 25th percentile
Q2 = second quartile = 50th percentile
Q3 = third percentile = 75th percentile

Question 6

Discrete data

Answer 6

Exact numbers (usually from counting)

Question 6

Interquartile range

Answer 6

Measure of dispersion (spread) of the data

Question 7

Continuous data

Answer 7

Any value in a certain range (can be decimal)

Question 8

Reliable data

Answer 8

Repeatable data

Missing data can affect reliability
Bias: you have results favouring one outcome over another. **We try to minimize bias.

Question 9

Sampling techniques

Answer 9

1. Simple random
2. Convenience
3. Systematic
4. Quota
5. Stratified

Question 10

Simple random sampling technique

Answer 10

Equal chance of choosing. Choose out of a hat, number generator, etc.

Ex. Poll students from school - # assigned to students, choose with a random # generator.

Question 11

Convenience sampling technique

Answer 11

Choose easiest people to sample: ask your friends etc. Problems? May not be representative of population

Question 12

Systematic sampling technique

Answer 12

Choose random starting point, use fixed interval.

Ex. Make a list of all students in a class, choose every 3rd student.

Question 13

Quota sampling technique

Answer 13

Sample sizing to who you’re polling

Ex. 55% girls, 45% boys in school, so sample should have those same %.

Question 14

Stratified sampling technique

Answer 14

Split into strata (smaller groups)

Ex. Choose half dp1, half dp2 students

Question 15

Outliers

Answer 15

We might want to remove values from a data set if they fall too far outside criteria

Outlier = more than 1.5(IQR) from nearest quartile.
- less than Q1 - 1.5(IQR)
- more than Q3 + 1.5(IQR)

Question 16

Standard deviation

Answer 16

How far values are from the mean.

Question 17

Variance

Answer 17

The square of standard deviation

Question 18

Frequency tables

Answer 18

Keeps track of not only how many times (frequency) it happens, but keeps a running total (cumulative frequency)

**Useful for finding percentiles, quartiles and median

Question 19

Interpolation

Answer 19

Use the x value with the equation

Question 20

Extrapolation

Answer 20

Use the y value with the equation

Question 21

Conditional probability

Answer 21

The probability of an event happening given that another event already occured.

Question 22

When to use binompdf

Answer 22

Tells you the probability of exactly “r” successes

binompdf (n, p, r)

where,

binompdf = exactly “r”
n = # of trials
p = probability of success
r = # of successes

Question 23

When to use binomcdf

Answer 23

Tells you the probability of up to “r” successes

binomcdf (n, p, r)

where,

binomcdf = up to “r” (cumulative)
n = # of trials
p = probability of success
r = # of successes

Question 24

Normal distribution curve

Answer 24

Area under curve

68% between μ ± σ

95% between μ ± 2σ

99.7% between μ ± 3σ

Question 25

Inverse norms only tell you about the area to the left