Last class Descriptive Statistics Excel and SPSS Tutorial (Tutorial 1) THIS CLASS Census Overview Normal Distribution Hypothesis Testing URBP 204 A Class 4 Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Census Overview Source: U.S. Census

Five Wounds Brookwood Terrace Project Census tract numbers , and lie fully within the FWBT area while part of census tract number falls within the FWBT area. Source: Mike Reilly, Instructor URBP 179, Fall 2004

Census Overview Go to: Go to: “American Fact finder” Go to “Maps” Go to “Reference Maps” Go to: Select a boundary grouping Select: 2000 Census Tracts and Blocks Select: CA as State and as Zip Code Go to: Reposition on… Select: A street address or zip code Type: “E St James and N 26TH St” under Street Address “San Jose” under City Choose “CA” under state Zoom out to 2.8 miles across How to obtain files for socio-economic, housing characteristics ? Datasets - Decennial Census – SF1 - Demographic (DP-1) and Housing (QT-H1). Also explore SF-2 and SF-3.

Normal Distribution Features: Mean, median, and mode are the same Symmetrical about the mean Tails are asymptotic- tails tend to reach x- axis, but never touch Example with Mean= 100 Standard Deviation = 10 Between mean and 1 std. dev (between 90 and 110) = 34.13% cases (on either side) - total 68.26% Between mean and 2 std. dev (between 80 and 120) = 47.72% cases (on either side) - total 95.44% Between mean and 3 std. dev (between 70 and 130) = 49.87% cases (on either side) - total 99.74% Go to the following link for a dynamic example: Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Z Score How to compare different distributions? Z = (X- X) / s z = z score X = raw score X = mean s = sample standard deviation Example: Variable: Height ; Other Examples: accidents per month; crimes reported per year; permits issued per year Raw score = 78 inches (6’ 6” feet) Mean = 72 inches (6 feet) s = 6 inches z = (78-72) / 6 = 6 / 6 = 1 That means 78 inches is 1 std. dev. above the mean; score is 1 z score above the mean. If raw score = 66 inches z= (66-72) / 6 = -6 / 6 = -1 That means 66 inches is 1 std. dev. below the mean; score is 1 z score below the mean. Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Z score continued Larger the z score, further away from the mean is the raw score % (50% + 34/13%) of all scores fall below z score of 1. For raw score of 78 inches, when the mean = 72 inches and s = 6 inches Probability of the score greater than 78 inches is 16% (100-84). Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Hypothesis Does knowledge of good examples of high density residential development have an effect on a person’s attitude towards high density residential development as measured by the density attitude scale? - Research question Null hypothesis: no effect; no relationship between variables H 0 : Ц before = Ц after Research Hypothesis: effect; there is relationship between variables H 1 : X before = X after Non- directional research hypothesis or H 1 : X before X after Directional research hypothesis Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Null and research hypothesis Null hypothesis : equality Research hypothesis: inequality Null hypothesis : population Research hypothesis: sample Null hypothesis : indirectly tested (as don’t survey the entire population) Research hypothesis: directly tested (as the entire sample is included in the analysis) Null hypothesis : Greek symbols Research hypothesis: Roman symbols Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Characteristics of a good hypothesis: Declarative, clear and forceful; not a question Presents an “expected” relationship between variables Reflects the theory / literature Brief and to the point Testable Note: the class notes summarize Salkind (2004) Chapters 6 to 8

Statistical Significance Research question Does knowledge of good examples of high density residential development have an effect on a person’s attitude towards high density residential development as measured by the density attitude scale? Research hypothesis Knowledge of good examples of high density residential development positively effects a person’s attitude towards high density residential development as measured by the density attitude scale. How can we be sure that the increase is not by chance but only because of watching the movie? - Level of risk associated with being incorrect Significance level: “risk associated with not being 100% confident that what you observe in an experiment is due to the treatment or what was being tested..” (Salkind, p.143) Note: the class notes summarize Salkind (2004) Chapters 6 to 8

4 Possibilities Null hypothesis is true and you fail to reject (Salkind book – accept) it. Great! There was actually no difference in scores in the entire population and you also found none in your sample. Null hypothesis is true but you reject it – Type 1 error If level of significance = 0.05: 5% chance that you will reject the null hypothesis when it is true. Made a mistake! Actually there was no difference between before and after score in the entire population but you found a difference in your sample. Null hypothesis is false and you fail to reject (Salkind book- accept) it - Type 2 Error. Accept equality when inequality exists. As sample size increases the probability of type 2 error decreases. Other reason: sample not representative of the population. Made a mistake! Actually there was a difference in scores in the entire population, but you did not find any difference in your sample! Null hypothesis is false and you reject it Great! There was a difference in scores in the entire population and you found a difference in your sample too. Note: the class notes summarize Salkind (2004) Chapters 6 to 8