Statistics Descriptive

Describes descriptive statistics stops right before probability

What is Descriptive Statistics

Organizing and summarizing data using graphs and numbers

what topics consist of descriptive statistics

Data Summary graphs
Measures of central tendency
Measure of variability

What is Measures of central tendency ?

the typical behavioral response from the data set

What are the three measure of central tendency

Mean , Median , Mode

Arithmetic Mean

average tries to describe typical behavior of the data​, sensitive to outliers

Median

middle number of a sorted array , is not swayed by outliers

Mode

most frequent data point in a array of data describes most common

What is measure of variability

describes how spread/scattered out the data points are from each other and from the center of the data

Low variability

data points are closer together, near the center, might have more consistency and predictability

High Variability

data points are spread out , farer from the center, inconsistency larger diversity in the data, less predictability

What are the measures of variability

Range, Standard Deviation, Variance, IQR, Mean absolute deviation

Variance

population or Sample, measure the average squared deviation of how spread out the data is from the mean

Standard Deviation

measures out on average how spread out the data is from the mean , square root of variance.

Range

Max high - min low values in a data set , sensitive to outliers

Mid Range

Average of high and low
/
count of 2

Inter Quartile Range

measures the spread of the middle of the data
less effected by outliers in the data
Q3 - Q1 = IQR

Outliers Formula

largely outside the average of the data ,
Q1 - 1.5 * IQR
Q3 + 1.5 * IQR

Whats Q1 in IQR and how to calculate it

its 25% of the data the lower bound,
median of the lower half of the data excluding if odd

What is Q3 in IQR and how to calculate it

75% of the data, find the median of the upper half of the data

Mean absolute deviation

measures on average how spread out the numbers are from the mean with absolute difference

relative frequency

proportion (percentage of the total that a particular group makes up

purpose of relative frequency

shows how common something compared to the whole data set, category comparisons

cumulative frequency

sum of the frequencies up to that point in the data (total up to a certain data point )

use of cumulative frequency

tells how many values fall below or at a certain point helps finds percentiles ,medians

Example of relative frequency

check notion

example of cumulative frequency

check notion

z score

tells you how many sd’s a value is from the mean, uses the z table
standardizes a raw score

z table

a cummalitve relative frequency (area under the curve to the left of a z score
tells you a percents of data vals less than the zscore (fall under

ztable practice

check notion
given a data point, a mean , and a sd

a normal distribution

a bell curve (symmetrical ) . mean is equal to median

Empirical Rule

a normal distribution:
68 % of the data follows 1sd
95 % of the data follows 2 sd
99/7 % of the data follows 3 sd

What is a density curve ?