# UMass Amherst PSYCH 241 - study guide for exam 2 (4 pages)

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- University of Massachusetts Amherst
- Course:
- Psych 241 - Meth Inqry in Psych

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241 Study Guide for Exam 2 Example Questions Be prepared to identify and sequence the seven overarching stages of theory driven research 1 Theory or general problem of interest research question 2 Generate specific testable hypothesis 3 Design study and evaluate ethics 4 Conduct study so as to achieve unambiguous results evaluate internal external validity 5 Collect and summarize data descriptive statistics 6 Draw conclusions from these analyses inferential statistics 7 Reject modify support original hypothesis What are the three steps of data analysis and interpretation 1 Get to know the data inspect data carefully identify errors in data consider whether the data makes sense or not 2 Summarize the data use descriptive statistics central tendency variability effect size and graphical displays of data 3 Confirm what the data reveal representative of the population mean perform inferential statistics analysis What does the use of statistical software packages mean for the researcher Means researchers do few calculations but need strong understanding of methods Design Analysis What are the three things you should do in getting to know your data Inspect data carefully identify errors in data consider whether the data makes sense or not Be prepared to describe the three measures of central tendency we discussed Mean sum of scores divided by number of scores arithmetic average Median middle point of frequency distribution score that splits the distribution in half Mode most frequent score in distribution can be more than one mode Be prepared to describe the four measures of variability we discussed Range of scores difference between highest lowest max min Variance s 2 sum of the squared differences between X1 and X divided by sample size n 1 Standard Deviation SD or s how far on average a score x is from the sample mean X Measures of Effect Size formula for Cohen s d d X1 X2 SD How is the standard error of the mean related to the standard deviation Measures how well the sample mean estimates the population mean standard deviation of theoretical sampling distribution of means How does increasing the sample size influence the standard error of the mean specifically Sample size produces tighter estimate of the standard error of the mean What does the standard error of the mean tell us about the population mean Measures how well the sample mean estimates the population mean What are we assessing with effect size measures Can compare across different studies form of meta analysis What measure of effect size do we use for the comparison of two means Cohen s d What does a confidence interval tell us about the population mean A range of values which we state with a certain degree of confidence includes the population mean How does increasing the sample size influence the confidence interval specifically What are we trying to accomplish with the three stages of data analysis Decide whether results support hypothesis or not What is the primary goal of a null hypothesis significance test NHST To determine whether there are differences among conditions What are the two steps of NHST What does the probability value tell us Step 1 Assume conditions do not differ Step 2 Compute appropriate statistic to test for condition differences t test or ANOVA probability value tells us if statistically significant When do we reject the null hypothesis When do we accept the null hypothesis Reject null hypothesis when the outcome has a small likelihood of occurring never accept the null hypothesis If the observed p value is 0 5 why don t we accept the null hypothesis Researchers are tentative about conclusions errors can occur other hypotheses may exist findings support the hypothesis but do not prove it What do we mean by Type 1 error What do we mean by Type 2 error Type 1 error hypothesis rejected when actually true no difference Type 2 error hypothesis not rejected when actually false difference What do we mean by experimental sensitivity and how can we increase this Likelihood that an experiment will detect the effect of an independent variable when the independent variable had an effect hypothesis is false sensitivity increases with good research design and methods What do we mean by power and what three factors affect the power of a statistical test Power of statistical test level of significance alpha size of effect for independent variable on dependent variable sample size Why do repeated measures designs often lead to greater experimental sensitivity Minimize error variance reduce noise What is the logic of the ANOVA and how does the true experimental design relate to this Identify sources of variance in data primary vs error When would you use the ANOVA approach rather than the t test When you have more than 2 levels of an independent variable Be prepared to present and describe the conceptual formula for the ANOVA F variation between groups variation within groups What do we mean by partitioning the variance and how is this used in ANOVA Split total to due to IVa and chance and due to chance Be prepared to identify the four designs we discussed and to construct their skeleton tables 1 way Independent Groups Source df IVa a 1 Error a n 1 Total an 1 1 way Repeated Measures Source df IVa a 1 Subjects n 1 Error a 1 n residual 1 Total an 1 2 way Independent Groups Factorial Source df IVa a 1 IVb b 1 IVa IVb a 1 b 1 Error ab n 1 Total abn 1 2 way Mixed Factorial Source df IVa a 1 Error independent group factor a n 1 IVb b 1 IVa IVb a 1 b 1 Error for Repeated Measures a n 1 b Interaction 1 Total abn 1 Be prepared to extract the important information from summary tables for the four designs Above Be prepared to calculate the Mean Square values and F ratios in an ANOVA summary table Mean Squares sum of squares degrees of freedom F ratios Mean Squares of IV Mean Squares of error When would you use confidence intervals with the ANOVA approach Can plot the means along the confidence intervals to judge where differences are likely to exist When would you use post hoc test with the ANOVA approach Why would you do this To compare multiple pairs of means repeated measures ANOVA What can you tell me about family wise error and how to minimize it The probability of making one or more false discoveries Type 1 errors among all the hypotheses when performing multiple hypotheses tests keep below alpha level of significance to minimize What does eta squared tell us about the independent variables Indicates the proportion

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