Essential Questions EQ 1-5: How do psychologists draw appropriate conclusions about behavior from research? **Make sure in their do now they grab a graphic organizer! And stand. Dev. handout

Do Now: Take the 3 handouts, and go over your homework with your table. Make sure you all agree on the answers!

The Science of Psychology Approaches to Psych Growth of Psych Research Methods Statistics Descriptive Correlation Experiment Case Study Survey Naturalistic Observation Inferential Ethics Sampling Central Tendency Variance Careers We are here

Why do we need statistics in psych?!

Descriptive Statistics: Central Tendency  Mean, median, and mode skewed distributions Variance  Range standard deviation normal distributions Inferential Statistics:   Statistical significance t-test and the p-value Outline of what we are doing today. Explain the difference between descriptive and inferential. Descriptive stats: describe data for the targeted population. If I study people here at RHS, when I report the data, it only describes people here at RHS. Can be used with more than experiments—surveys, correlations, etc. nat. obs. Maybe copy this down on the side-board so they can follow along!

Statistical procedures analyze and interpret data and let us see what the unaided eye misses. Make sure I highlight that data presentation is crucial. It’s SO easy to “lie” with stats.

Central Tendency Tendency of scores to congregate around some middle variable A measure of central tendency identifies what is average or typical in a data set On their G.O.

Measures of Central Tendency Mode: The most frequently occurring score in a distribution. Mean: The arithmetic average of scores in a distribution obtained by adding the scores and then dividing by their number. Median: The middle score in a rank-ordered distribution. OBJECTIVE 17| Describe three measures of central tendency and tell which is most affected by extreme scores.

Practice: What is the mean, median, & mode of the following distribution: 1, 6, 3, 12, 8, 11, 9, 10, 4, 6 Have answers written down

Normal Distributions The distribution of data also gives us key info. We know that many human attributes… e.g height, weight, task skill, reaction time, anxiousness, personality characteristics, test data, attitudes, birthdays, etc. …follow a normal distribution. Emphasize that would in our class now too! 10

Start dice activity! –use Vita hand out as a reference for me.

Practice: Imagine that you are a golfer of above-average ability and that you have the opportunity to play the greatest golfer in the world (say Tiger Woods). If you want to maximize your slim chance of winning, how much golf would you elect to play, given the choices of 1, 18, 36, or 72 holes?

A certain town is served by two hospitals A certain town is served by two hospitals. In the larger hospital about 45 babies are born each day, and in the smaller hospital about 15 babies are born each day. Although the overall proportion of boys is about 50 percent, the actual proportion at either hospital may be greater or less than 50 percent on any day. At the end of a year, which hospital will have the greater number of days on which more than 60 percent of the babies born were boys? (a) the larger hospital (b) the smaller hospital (c) neither--the number of days will be about the same (within 5 percent of each other)

Negatively Skewed Positively Skewed                  Positively Skewed Use test data as an example (like 1st unit test) Look where the tails are pointing!

Central Tendency Let’s look at the salaries of the employees at Dunder Mifflen Paper in Scranton: $25,000-Pam $25,000- Kevin $25,000- Angela $80,000- Jim $100,000- Andy $100,000- Dwight $300,000-Michael The median salary looks good at $80,000. The mean salary also looks good at about $93,500. But the mode salary is only $25,000. Maybe not the best place to work. Then again living in Scranton is kind of cheap. Have them calculate first! These results are -ish

The mean doesn’t work in a skewed distribution I can lie to Spiller about your test scores. Maybe you all fail, but a few get super high scores, then it pulls up the average and everything looks great  can do the same with class average of grades in general The Median is much better

Descriptive Statistics: Central Tendency  Mean, median, and mode skewed distributions Variance  Range standard deviation normal distributions Inferential Statistics:   Statistical significance t-test and the p-value Outline of what we are doing today. Explain the difference between descriptive and inferential. Maybe copy this down on the side-board so they can follow along!

Two Measures of Variation Range: The difference between the highest and lowest scores in a distribution. 7, 98, 46, 38, 54, 78, 9, 5, 45, 23 On their graphic organizer. Make sure I have range written down! Psychology 7e in Modules

Standard Deviation: the variance of scores around the mean. The higher the variance or SD, the more spread out the distribution is. Do scientists want a big or small SD? Shaq and Kobe may both score 30 ppg (same mean). But their SDs are very different. Standard deviation measures the average distance between each score and mean in the data set.

Normal Distribution So let’s go back to our normal curve and see how it looks with standard deviations. So let’s look at how a normal distribution is set up so we can understand more about standard deviation. Have them copy this down and memorize it!! Also discuss z-scores. Remember a third for the first standard dev., then ½ of that is 15 (14%), then the 2%. 20

Measures of variability: how similar or diverse a set of scores are Measures of variability: how similar or diverse a set of scores are. I can give a test to 4th hour and 6th hour, and they both might have a mean of 80, and you might say, wow we did equally well. But that’s not necessarily true. The standard deviations could be different, thus effecting the shape of the bell curve (steep or flat)

Standard Deviation in Action A couple needs to be within one standard deviation of each other in intelligence (10 points in either direction). —Neil Clark Warren, founder of eHarmony.com 22

Normal Distribution So let’s look at how a normal distribution is set up so we can understand more about standard deviation. Have them copy this down!! Also discuss z-scores 24

Practice Prob: What is the standard deviation for the numbers: 75, 83, 96, 100, 121, and 125? Use the graphic organzier!

Descriptive Statistics: Central Tendency  Mean, median, and mode skewed distributions Variance  Range standard deviation normal distributions Inferential Statistics:   Statistical significance t-test and the p-value Outline of what we are doing today. Explain the difference between descriptive and inferential. Descriptive stats: describe data for the targeted population. If I study people here at RHS, when I report the data, it only describes people here at RHS. Can be used with more than experiments—surveys, correlations, etc. nat. obs. Maybe copy this down on the side-board so they can follow along!

Inferential Statistics You are trying to reach conclusions that extend beyond just describing the data. Inferential stats allow us to apply the research data to the entire population, not just the sample. I can apply RHS data to all high school students in the US. ONLY USED WITH EXPERIMENTS (CAUSE & EFFECT)

Does caffeine improve our reaction time? We recruit 40 people and give (random assignment) 20 a caffeine pill (experimental group) 20 a sugar pill (control group) We give them a brief reaction time test and record the results. Yes, group results are different. . . 28

Why can’t I be done?! You don’t know if that difference was due to your IV (caffeine) or just dumb luck. You have to be sure that the results are statistically significant

Statistical Significance *You can never 100% fully prove anything in science, because you can never know if it was 100% not due to chance *You can only reject the null hypothesis, which is the opposite of your hypothesis *Statistical Significance: Means that the results of the experiment were most likely NOT due to random CHANCE/dumb luck. p-value < .05% *(never a 0% p-value) BUT if the p-value is less that .05%, you can be confident enough to disprove null hypothesis (statistically significant) Use the caffeine example that we were doing the class before to give an example. More notes in Stats packet practice. Can have any confidence interval, but science only accepts less than 5% 30

T-test results Does caffeine improve our reaction time? Caffeine condition has a lower mean RT. We run a t-test on our samples and get: p = 0.039 Can we be confident that the difference in the data is not due to chance? Reject the null!! 31