PSYC 203 1st EditionExam # 2 Study Guide Lectures: 12 - 20Lecture 12 - Construct Validityo Validity of a construct  Construct: hypothetical idea, like extraversion or happinness- Convergent and Discriminant Validityo Associations Between Different Methods of Assessing the Same Construct. Confirmation of the Measurement of the Construct using Multiple Methods.o Distinctiveness of Constructs. This is indicated by a lack of association between measures of different constructs. Ex: being able to differentiate between anxiety and depression- Relation between Reliability and Validityo Something can be reliable without being valid o For ex: your shoe size and IQ both remain the same but this doesn’t mean that they are correlated in any way - How to specify Null and Research Hypotheses o The null embodies the idea of no association while the research embodies the ideathat there is an association between two given factors Lecture 13- Directional versus Non-Directional Hypotheses o Directional: indicates that something is positively or negatively assocated o Non-directional: only states that factors are associated, but doesn’t predict how - Attributes of good hypothesis (book)o Framed as a declaration, not a questiono Specifico Based on scientific literature o Concise o Testable - Attributes of the Normal Curve o Mean, median, mode are equalo Perfectly symmetricalo Asymptotic  Tails get closer and closer to the x-axis but never touch it Lecture 14-15 no classLecture 16- Probability and the Normal Curve o The normal curve serves as a foundation for determining probability for many statistical tests in 203.o Probability decreases at the tails - z-scoreso z (x −x)/s- z-scores and Percentilesoo If we know that each section contains a certain percentage of the cases, then we also know the chances of obtaining scores.o Example: What is the probability of getting a score of 110 or higher? (Mean = 100, SD = 10) 13.59+2.15+.13=16% • 100–(50+34.13)=16%- Lecture 17 (September 7)-- Using the Normal Curve Table to solve problemso These give you the percentage associated with individual z-scores o You can use this to figure out other probability percentages - Type I and Type II Errorso type 1 error: the probability of rejecting a null hypothesis when it is trueo type 2: the probability of accepting a null hypothesis when it is false - Confidence Intervals (book)o the best estimate of a range of the population value given the sample value - When to use the z-test Testo To compare your sample results to the populationLecture 18- The Famous 8 Steps Applied to this Testo State the hypothesiso Set the significance level (alpha)o Select the appropriate inferential test statistico Use the selected inferential test to compute a test statistic. The test statistic is a single number that comes from the formula for the specific test. These test statistics can be used to compute p- values.o Determine the CRITICAL VALUE for the test statistic. This is the minimum value needed to reject the null hypothesis. In other words, this is the value needed to REJECT THE NULLo Compare your obtained test statistic to the critical value.o If the obtained value is bigger than the critical value, Reject the Null Hypothesis When the obtained value is bigger than your critical value, your p-value is smaller than your cutoff.o If the obtained value is smaller than the critical value, Fail to Reject the null hypothesis This means your p-value is bigger than your cutoffLecture 19- How to Calculate the SEM (Standard Error of the Mean)o (X−μ)/ SEM=zo Xbar = the mean of the sample o Mu = population averageo SEM = standard error of mean- How to Interpret the Test Statistico z tells us what test was used o the number before p tells us the number obtained using the formula o p tells us that we rejected or accepted the null Lecture 20- Monty Hall Problemo You are on a game show. You have a choice of three doors: Behind one door is a car whereas behind the other two are goats. You pick Door No. 1. The host, who knows what's behind the doors, opens Door No. 3 to show you a Goat. He then says to you, "Do you want to pick door No. 2 or stay with No. 1?" Is it to your advantage to switch your choice?o Yes, because the odds are better - Definition of Statistical Significance o We will use the term statistically significant or sometimes just significant in 203. This word has a technical meaning different from common language.o The observed result (e.g., the observed mean difference) is unlikely to occur if the NULL hypothesis was TRUE.o There is a statistically significant difference between the two groups.- Definition of a p-valueo Probability