Unit 1 Stats Vocab/Study (One-Var Data)

statistics

values that describe a sample

parameters

values that describe a population

discrete variables

variables which take on values w/ gaps between them

continuous variables

variables which take on any value in an interval

what aspects of the shape of a distribution do we address?

symmetry, shape, skew, modality, and uniformity

skewed left

tail is to the left

negatively skewed

tail is to the left

skewed right

tail is to the right

positively skewed

tail is to the right

dotplot

simple graph in which data values are plotted above the corresponding #s on a # line

stem and leaf plot

just know how to read it; 10s value on one side of line, various 1s values on other side

what’s the difference between a bar chart and a histogram?

a bar chart is used for CATEGORICAL data, while a histogram is used for QUANTITATIVE data

resistant statistics

a statistic which isn’t influenced dramatically by extreme values (e.g. median)

standard deviation

square root of the variance

variance

sum of the squared distances of data values’ distance from mean, divided by n-1 (known as s^2 on form. sheet)

Interquartile Range (IQR)

spread between the medians of the upper and lower halves of the distribution (Q1 & Q2)

1\.5 IQR Rule

Any value 1.5 IQRs below Q1 or 1.5 IQRs above Q2 is considered an outlier.

5-Number Summary

minimum value, Q1, median, Q3, maximum value

boxplot

graphical version of 5-# summary, with whiskers going from min to max, and a box going from Q1 to Q2 with a line for the median. outliers are included as dots (WHISKERS END AT LARGEST VALUE THAT ISN’T AN OUTLIER)

percentile rank

the proportion of terms in a distribution less than a given term (e.g. a # that is at the 75th percentile is greater than 75% of the terms in the distribution)

what is the empirical rule for the Normal model?

68-95-99.7 (68% of data are within 1 SD of mean; 95% w/in 2; 99.7% w/in 3)

standardized score/value

z-score (standardized b/c z-scores can be compared across multiple distributions etc. & always mean same thing)

area for invnorm is…

the area to the left of the #