Chapter One.
Individuals
The objects described by a set of data. Individuals may be people, but they may also be animals or things.
How to analyze overall pattern.
Describe shape, center, and spread.
Two types of quantitative variables.
Continuous or discrete
Difference between a bar graph and a histogram.
A histogram displays the distribution of a quantitative variable. The horizontal axis of a histogram is marked in the units of measurement for the variable. A bar graph compares the size of different items.
Seasonality.
A pattern that repeats at periodic intervals over time.
Spread describes what two values?
Minimum and Maximum.
Timeplot
Plots each observation against the time at which it was measured.
Midpoint
The value with roughly half the observations taking smaller values and half taking larger values.
Two types of categorical variables
Nominal or ordinal.
Nominal vs. ordinal variables
Nominal variables are purely qualitative and unordered, like flower color, whereas ordinal data can be ranked, such as with star ratings or the Likert scales commonly used in psychology.
On a timeplot, where is time plotted?
On the horizontal axis.
How to describe deviations.
Outliers.
Two things you look for when analyzing a graph.
Overall pattern and any deviations.
Categorical variable
Places an individual into one of several groups or categories.
Differences between symmetry and right/left skew.
Right skew: right extends further. Left skew: left extends further.
Continuous vs. discrete variables.
Some quantitative variables, like stem length, are continuous variables that can take any real numerical value over an interval. Discrete variables, on the other hand, are quantitative variables that can take only a limited, finite number of values, like the number of petals in a flower.
Two parts of the stemplot
Stem and leaves. Leaves are the final digit.
Difference in spacing on the graph between a bar graph and a histogram.
Always make sure to leave some blank space between the bars in your bar graphs to separate the items being compared. In contrast, always draw histograms with no extra space between consecutive classes, to indicate that all values of the variable are covered.
Variable
Any characteristic of an individual.
Which graph is preferred with stats: Bar graph or pie chart?
Bar graph
Two types of graphs used for categorical variables and their respective summaries.
Bar graphs and pie charts.Summaries: counts and percentages)
Two types of variables?
Categorical and quantitative.
Three steps to make a histogram
Divide the classes. Count the individuals. Draw the histogram.
A simple version of a histogram is called?
Dotplot.
Small quantitative data sets use what two types of graphs?
Dotplots and Stemplots.
Two types of graphs used for quantitative variables and their respective summaries.
Dotplots, stemplots, histograms, boxplots. Summaries: mean, median, mode, std deviation, quartiles)
What is the most common graph used with quantitative variables?
Histogram
Each data set contains information about what?
Individuals.
Quantitative variable
Takes numerical values for which arithmetic operations such as adding and averaging make sense. The values of a quantitative variable are usually recorded in a unit of measurement such as seconds or kilograms.
Distribution
Tells us what values it takes and how often it takes these values.
Two ways to describe trends.
Upward or downward.