Transcript Statistics in a NutShell

Statistics in a Nutshell
Interested in Entire Population
 Large Population = Expensive Surveys
 Sample a Small Group

– Infer Population Characteristics
– from Sample Characteristics
Examples
Exit polls on election day
 Marketing surveys for new products
 Medical trials for new vaccines
 Neilson ratings of television shows
 Air measurements for pollutants

Definitions
Population --- Universe (Entire Group)
Parameter
Numeric Characteristic of a Population
Average, Variance, Standard Deviation, etc
Sample --- Subgroup of the Population
Statistic
Numeric Characteristic of a Sample
Average, Variance, Standard Deviation, etc
Sampling
Sampling is faster, cheaper, easier.
Sampling
Sampling is faster, cheaper, easier.
Hope, that the sample is representative of the
population; and therefore, the sample statistic
is an accurate estimate of the population
parameter.
Sampling
Sampling is faster, cheaper, easier.
Hope, that the sample is representative of the
population; and therefore, the sample statistic
is an accurate estimate of the population
parameter.
If the sample is not representative of the
population, then all bets are off !
Statistics

Descriptive Statistics
– Collecting and Analyzing Data
– “Tells a story about the numbers”

Inferential Statistics
– Drawing conclusions about a population
Descriptive Statistics

Measures of Central tendency
– Mean (Arithmetic Average)
– Median (Middle Value)
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Measures of Variation
– Variance
– Standard Deviation
Measures of Central Tendency

Mean
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Arithmetic Average
Balance Point
Basis for other statistics
Influenced by extremes
Median
– Middle Value
– Different Balance Point
– Not influenced by extremes
Important Statistics

Mean
– Tells where the data is centered

Standard Deviation
– Tells how far the data is spread out
Family Reunion
Babies, youngsters, teenagers
young adults, middle-aged parents
grandparents, great grandparents
Average Age ?????
Standard Deviation ?????
15th High School Reunion
Average Age ?????
Standard Deviation ?????