Ch.4 Flashcards
What falls under qualitative data? (3)
- absolute numbers
- percentages
- proportions
What falls under quantitative data? (3)
- summary measures of location
- summary locations of spread
- summary measures of position
What are summary measures of location? (3)
- mean
- median
- mode
What are summary measures of spread? (4)
- Range
- Variance
- standard deviation
- coefficient of variation
What are summary measures of position? (2)
- Percentiles
- Quartiles
Define summary measures of location:
summarizes information and indicates which numbers tend to aggregate the values of the variable
-tendency for the values of a random variable to cluster round its mean, mode, or median.
What is another name for summary measures of location?
central tendency measures
Mean of a population is represented by what character?
μ
What is the median?
middle value
What is it called when there are two modes?
bimodal distribution
What is the spread/variability?
Measures of dispersion.
Variability = indicators
of the homogeneity of the values
- more distant from mean = data is more dispersed
- higher value of dispertion = greater variability = less homogenous
What is range?
difference between upper and lower value
What is average deviation?
measures variability of data around the mean/avg distance to the mean
-add all the distances of each observation to the mean divided by number of observations
When do you use variance versus sample variance?
sample is a sample of the population
Variance is total population
The units of standard deviation are the same or different than the variable?
same
What is the coefficient of variation?
percentage of the mean that the standard deviation represents
Why is coefficient of variation useful?
-allows comparison of mean and variance of variables measured in different units to see which varies more
Define the summary measures of position
indicate which place or position a certain value of the variable occupies within the set of observed values
-divide set of observations into equal parts
What is a percentile?
indicate the
percentage of values that are equal to or
lower than the value we have measured
ex. height of 130 cm being in the
percentile 60, it means…that 60% of children of that age in this
population measure equal to or less
When do we use percentiles?
to standardize anthropometric measurements ex. weight and height
Define Chebyshev’s inequality
regardless of how data are
distributed, at least 75% of the values of the variable
are included in [μ±2 SD]
ex. If the mean is 34 and the standard deviation is 2, at
least 75% of the values are between 34-4 and 34+4, this is
between 30 and 38
What happens if the mean and medial are equal?
the
distribution is symmetrical
When do we use range?
when we should
emphasize the extreme values
What graphs do we use for qualitative variables? what else do we use these for? (2)
- Bar chart
- Pie chart
- also quantitative discrete variables
What graphs do we use for quantitative continous variables? (2)
- histograms
- frequency polygons
What do we use a histogram for?
frequency of the values displayed by using bars of different heights
How does a histogram differ from a bar chart?
histogram groups values into ranges
What do we use a frequency polygon for?
- understand shape of variable distribution
- useful to visualize frequency changes
