Презентация Getting your data: Sources and samples онлайн

Содержание слайда: Getting your data: Sources and samples

Содержание слайда: Sources of psychological data and Data collection methods Data sources

Содержание слайда: Why experiment is not a method of data collection?

Содержание слайда: Data collection exercise - 15 mins - In groups of 4 think of a Research Question/ Hypothesis What type of data is the most suitable for your RQ or H? What data collection method is the most suitable? WHY?

Содержание слайда: Sample

Содержание слайда: Sample and distribution What is distribution?

Содержание слайда: Descriptive statistics…

Содержание слайда: Exercise A survey of 20 students was conducted to find out how many books they had read during the past three months (including books for school). The results from those 20 students are shown below. Find the mean, median, and mode for this data. 2, 4, 5, 1, 3, 2, 5, 6, 1, 2, 4, 3, 6, 10, 12, 10, 2, 8, 6, 7 Answers: Mean = 4.95. Median = 4.5 Mode = 2.

Содержание слайда: Normal distribution Properties of any theoretical normal distribution: 1) The curve never approaches horizontal axis. 2) Symmetrical around the mean. 3) Skewness = 0 and kurtosis = 0. Standard normal distribution is a special case of theoretical n.d. with 2 properties: 1)  = 0,  = 1; 2) area under the curve = 1, and integral of (-∞; z] can be interpreted as probability of finding values equal to or below Z.

Содержание слайда: Normal distribution

Содержание слайда: Where is NORMAL distribution?

Содержание слайда: What do we know about STANDARD normal distribution? 1) The curve never approaches horizontal axis 2) Symmetrical around the mean 3) Skewness = 0 and kurtosis = 0 4) Mean = 0, SD = 1 5) Mean= mode= median =0

Содержание слайда: Why is it important to know what kind of distribution your variables have?

Содержание слайда: Descriptive statistics…

Содержание слайда: Are you tall?

Содержание слайда: When you know so much about distributions, you can compute a height distribution in your group

Содержание слайда: When you know Mean and SD, you can estimate whether you are tall or not

Содержание слайда: Is this result applicable in other groups? Are you tall in other groups? In HSE? In Russia? To answer this question we should use standard scores

Содержание слайда: Standard scores (Z-scores)

Содержание слайда: Standard normal table Shows you a PROBABILITY that all observed values in your sample are lower than Z

Содержание слайда: What is the probability to find people taller than you in… …Guatemala? Mean = 147.3 cm SD = 6.3 your Z = (your cm - 147.3)/ 6.3 Then look in Z-table

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Содержание слайда: Sample size and standard error We know M and SD in your group And we know M and SD in Guatemala

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Содержание слайда: Why do bigger samples provide better estimation?

Содержание слайда: Sampling strategies Probability strategy

Содержание слайда: Exercise: Match the statement with the appropriate term

Содержание слайда: I want to study cultural differences…/ I want to study how culture influence… This is possible only with representative samples collected in few countries!!!! A non-representative or a sample from 1 country only cannot help you with this kind of RQ Open access data: European Social Survey http://www.europeansocialsurvey.org/ World Values Survey http://www.worldvaluessurvey.org/wvs.jsp European Values Survey http://www.europeanvaluesstudy.eu/

Содержание слайда: Recommended reading: Howitt & Cramer, 2011, p. 232-246 (Samples). Supplementary reading: Bakeman, 2000 (Chapter 7 in Reis & Judd, 2000) (Observation) Cramer, 2007 (in Robins, Fraley, Krueger, 2007) (Archival method) Diamond & Otter-Henderson, 2007 (in Robins, Fraley, Krueger, 2007) (Physiological measures) Fraley, 2007 (in Robins, Fraley, Krueger, 2007) (Internet studies) Wilkinson, Joffe, & Yardley, 2004 (Interviews and focus groups)

Содержание слайда: Why Standardize ... ? Example 2. Here are the students results (out of 60 points): 20, 15, 26, 32, 18, 28, 35, 14, 26, 22, 17 Most students didn't even get 30 out of 60, and most will fail. The test must have been really hard, so the Prof decides to Standardize all the scores and only fail people 1 standard deviation below the mean. How many students will fail? Answer: The Mean is 23, and the Standard Deviation is 6,6, and these are the Standard Scores: -0,45, -1,21, 0,45, 1,36, -0,76, 0,76, 1,82, -1,36, 0,45, -0,15, -0,91 Only 2 students will fail (the ones who scored 15 and 14 on the test)

Содержание слайда: Next time Psychological measurement: Psychometrics and psychophysics