1. STATISTICS

2. What is the difference between descriptive and inferential statistics? Descriptive Statistics: Describe data Help us organize bits of data into meaningful patterns and summaries Tell us only about the sample we studied Inferential: Allow us to determine whether or not our findings can be applied to the larger population from which the sample was selected

3. What is the difference between a frequency polygon and histogram? Frequency polygon = line graph Histogram = bar graph Charting HOW OFTEN a score occurs Frequency (number of times something occurs) is always on the y axis

4. Why is the mean not always a “good” number to use to represent our data? Does not take into account extreme outliers Bill Gates walks into a coffee shop. The average income of all patrons soars. Median wealth remains unchanged. 19/20 of your friends have a car valued at $12,000, but another has a car valued at 120,000 Mean is 17,400 Not best measure; median is better

5. What is the range? Distance between highest and lowest score Tells us how spread out our scores are Highest score – Lowest Score

6. Standard Deviation Tells us how clustered our scores are around the mean Average distance of any score to the mean Less variability = more confidence in our mean Example: Basketball player averages 15 pts a game Are you more confident if their range is Between 13-17 pts in first 10 games Between 5-25 pts in the first 10 games? Higher the standard deviation, the farther from the mean scores are and vise versa Calculated as the square root of the variance Variance will be given to you Standard deviation for variance of 25 is… 5

7. How much do employees at small businesses make? 40,000 45,000 47,000 52,000 350,000 Mean = 106,800 Standard deviation = 136,021; Average difference between a score and the mean is 136,021 Discard the extreme score, SD is now 4,966.56 Distribution of first four is tightly clustered, distribution of all five is spread out Standard deviation example

8. DRAW AND LABEL A NORMAL CURVE FOR INTELLIGENCE

10. Where are the mean, median, and mode on a normal curve?

11. Is the mean on a normal curve always 100? No. Doesn’t matter what number mean is 68% of all scores will still fall within one standard deviation above and below the average 96% of all scores will still fall within 2 standard deviations above or below the mean

12. Skewed distributions What if our data don’t follow a normal curve? Positively or Negatively skewed (hump isn’t in the middle)

13. Negatively (left) Skewed Distribution There are low outliers Hump is to the RIGHT Mean is brought down (to the left of the hump) Mode is ALWAYS at highest point Median is also lower than the hump

14. Positively (right) Skewed Distribution There are HIGH outliers Hump is to the LEFT Mean is brought UP (to the right of hump) Median is higher than hump Mode is ALWAYS the highest part of the hump

15. PRACTICE TIME

16. Which has the greatest standard deviation? A. 5, 10, 15, 20, 25 B. 2, 4, 6, 8, 10 C. 1, 7, 10, 18, 29 D. 1, 2, 3, 4, 5 E. 2, 7, 10, 11, 16

17. What is the range of the following scores? 5 8 9 2 10

18. The Mean for a test is 50. Standard Deviation is 5. What percentage of the scores are below 45? What percentage of the scores are above 60?

19. Used to compare scores from different distributions Can convert scores from the different distributions into z scores. Z scores measure the distance of a score from the mean in units of standard deviation Scores below the mean have negative z scores Scores above the mean have positive z scores Amy scored a 72 on a test with a mean of 80 and SD of 8, her z score is -1 Clarence scored an 84 on the test, his z score is +.5 Z-scores