Moving on to Descriptive Statistics

Measures of Centrality

Mean, Median, Mode

X_i

sample numbers

What is the mean?

the average

How to you calculate the mean?

sum of sample / n

The mean is also the expected value

True

x̅

mean

What is the median?

the 50^th percentile

How do you calculate the median?

Arrange the numbers in chronological order, then find the middle number(s)

True or false

If you have two number that fall in the median, you have two medians. 

False. You add the two number then divide by 2 to get the median 

What is the mode?

the most occurring number

How do you calculate the mode?

arrange the numbers in chronological order then, find the number that occurs the most

True or false

There only ever be one mode in a dataset

False. You can have multiple modes within a data set

What are the Measures of Dispersion?

Range, Standard Deviation, Variance

How many Measures of Dispersion are there?

3

Range

the distance form the largest number in the dataset from the smallest

How do you calculate the range?

X_max - X_min

Variance

The average of the squared differences of each data point from the mean of the dataset.

(X_i - x̅)²

the formula to calculate each individual data point variance

Total Variance

add up all individual sums for the variance to get the total, then divide by the sample size

Standard Deviation

The square root of the variance

How to calculate the standard deviation?

take the square root of the Variance

Order of operation

Symmetric

X_mean = X_median = X_mode