Quiz 1 Version 1 Version 2 Version 3 1. D A C 2. 3. B 4. 5. 6. 7. 8. 9. 10.

The Construction of Knowledge Building Reality The Construction of Knowledge

Issues of Validity and Reliability Validity: Accurateness, i.e., is the measure/instrument used actually measuring what the researchers want it to measure? Reliability: Repeatability, i.e., if another researcher repeated the study with the same method and a different representative sample from the same population, would they get the same results?

But is it Reliable?

Who Would You Vote For?

But are they Symmetrical?

Real Life Example

The Problem of Averages What information are we seeking when we ask for the average ?

The Standard Normal Distribution = Mean, Median, and Mode

An Illustration Averages (means) are highly sensitive to extreme values. Example: $40,000 $50,000 $80,000 $30,000 $20,000

Calculating Measures of Central Tendency Mean: =($20,000 + $30,000 + $40,000 + $50,000 + $80,000) / 5 = $44,000 Median $20,000 $30,000 $40,000 $50,000 $80,000 But…what if one person gets their dream job…

$500,000 $50,000 Mean: =($20,000 + $30,000 + $40,000 + $500,000+ $80,000) / 5 = $134,000 Median $20,000 $30,000 $40,000 $80,000 $500,000

Mode Median ($50,233) Mean ($67,609) Number of Individuals Income

Correlation and Causation

Determining Causation is Difficult Must explain away alternative causes Example: Gateway Drugs Marijuana Use Use of Harder Drugs Association with Hard Drug Users

Determining Causation is Difficult Must explain away alternative causes Example: Gateway Drugs Marijuana Use Use of Harder Drugs Peer Pressure

Interpreting Sampling Error As of September 23, 2008: Gallup Polls show 44% 47% ± 2% sampling error

Interpreting Sampling Error Sampling error is the variation you could expect from taking multiple random/representative samples If we want to generalize to the population of voters we must consider sampling error as follows: Between 45% and 49% of voters support Obama (47 ± 2) Between 42% and 46% of voters support McCain (44 ± 2) It is impossible to determine a leader with this data!

So…When Faced with Information… Is the sample representative of the population? Are the measures used valid and reliable? Have the correct statistical methods been applied and have they been interpreted correctly? Did they cite the mean when they should have used the median? Did they jump from correlation to causation? Was sampling error correctly interpreted?