# Recitation 2 Chapter 1-3

## STAT 113 Recitation Sections

### Wutao Wei

# Variables

- Quantitative variable: takes
**numerical** values for which **arithmetic** operations such as adding and averaging make sense. (Age, weight, height, score, etc.)
- Categorical variable: places an individual into one of several
**groups** or **categories** (Color, major, hometown, etc.)

# Data Collection

- Anecdotal evidence: a story from one person or just a few people, not scientific.
- Observational study: observes individuals and measures variables of interest but does not attempt to influence the responses.
- Experiment: deliberately imposes some treatment on indivivuals in order to observe their reponses.

# Types of samples

- Convenience sample: selection of whichever individuals are easiest to reach
- Voluntary response sample: consists of people who choose themselves by responding to a general appeal. (
**BIAS**)
- Random sample: gives all individuals an equal chance to be chosen

# Types of random sampling

- Simple random sample(SRS)
- Stratified random sample

# Problems with sample statistics

- Bias:
**center** of sampling distribution shifted from population parameter
- Variability: how
**spread** out the sampling distribution is for the statistic.

# Group discussion time

- Please do your worksheet by group

# 1960 Election

- According to Pollster.com the only
*true survey* that attempted to gauge the debate reactions among television and radio listeners was conducted on November 7, 1960 the day of the elections. Sidlinger and Company did a telephone sample survey in which 282 persons responded. Their survey said that 48.7 of the radio audience thought that Nixon won and 21 picked Kennedy; of the surveyed television audience 30.2 named Kennedy the debate winner with 28.6 picking Nixon. Also, they projected that 270 million watched the debates and 61.4 million listened to them on the radio. (From Media Myth Surrounding the 1960 Kennedy-Nixon Presidential Debates & the Boston Globe)