| Describing Data | Practice Problems |
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A categorical variable has qualitative properties; divide the cases into groups, placing each case into exactly one of two or more categories.
A quantitative variable measures or records a numerical quantity for each case. Numerical operations like adding and averaging make sense for quantitative variables.What is a categorical variable? A quantitative variable? What is a categorical variable? A quantitative variable? |
p-hat = 0.104
A survey conducted of 1780 randomly selected US teens aged 12 to 18 found that 185 of them say they spend more than four hours a day in social networks.
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Categorical: gender, smoke, award, phone number
Quantitative: exercise, gpa, tv, pulse
Determine which variables are categorical and quantitative:
Gender: M for male and F for female Smoke: Does the student smoke: yes or no Award: Award the student prefers to win - Academy Award, Olympic gold medal, or Nobel Prize Exercise: Number of hours spent exercising per week TV: Number of hours spent watching television per week GPA: Current grade point average on a 4-point scale Pulse: Pulse rate in number of beats per minute at the time of the survey Phone Number |
spider-man: 0.055
superman: 0.354 batman: 0.591
Of the 379 readers of comics who answered the question about what superhero they would prefer, 21 preferred Spider-man, 134 preferred Superman, and 224 preferred Batman. Round your answers to three decimal places.
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Histogram
Dotplot Boxplot
What are the graphical displays of quantitative variables?
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:)
Draw scatterplots and appropriate regression lines for the correlation values:
r = -0.9, r=0.03, r=0.56 Also, describe |
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"SOCS"
Spread: standard deviation, interquartile range, range Outliers/Other locations: max, min, first quartile, outliers, etc Center: Skew: Distribution, skewed to left or right
How can we describe data?
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min: 30
q1: 47 q2: 83.5 q3: 163
Find the five-number summary, outliers, and construct a boxplot
89, 47, 164, 296, 30, 215, 138, 78, 48, 39 |
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For Quantitative:
Mean Median Standard deviation Five-number summary IQR, Range For categorical: Proportion (and Frequency table)
What are the summary statistics of quantitative variables? Categorical variables?
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invNorm (0.25, 8, 1.5) = 6.988 pounds ~ 7 pounds
For TI-83 folks: invNorm (0.25, 8, 1.5, left)
Let's say that the weights of newborn baby boys have an approximately normal distribution. Mean is 8 pounds, standard deviation is 1.5 pounds.
One newborn baby has a weight at the 25th percentile. What is an approximation of this baby's weight? |
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