Data analysis in psychology OSU Exam 1 Questions Fully Solved.

Descriptive vs. Inferential statistics - correct answers Descriptive statistics organize, summarized and communicate a group of numerical observations. -Children given 0mg of sugar had an average of 17.20 minutes of activity, children given 20mg had an average of 17.27 minutes Inferential statistics use sample data to make estimates about the larger population, infer or make an intelligent guess about the population -The relation between sugar consumption and activity level is inconclusive or minimally related. Sample and population - correct answers A sample is a set of observations drawn from the population of interest. Researchers usually study a sample, but they are interested in the population. Population: preschool children Sample: 30 preschool children at Preschool Playland Discrete and Continuous variables - correct answers Discrete variables can take on only specific values (e.g. whole numbers); no other values can exist between these numbers. -For example, if we measured the number of times someone wakes up early in the week, the only possible values would be whole number. (nominal and ordinal variables) Continuous variables can take on a full range of values (e.g. numbers out to several decimal places); an infinite number of potential values exist. -For example, a person might complete a task in 12. seconds or a shark might be 13.85 feet long. (interval and ratio variables) Scales of Measurement: -Nominal -Ordinal -Interval -Ratio (Scale) - correct answers A nominal variable is a variable used for observations that have categories or names as their values -Example, when entering data into a statistical computer program, a researcher might code male as number 1 or male as number 2 Ordinal variables are used for observations that have rankings as their values (i.e. 1st, 2nd, 3rd) Interval variables are used for observations that have numbers as their values; the distance (or interval) between pairs of consecutive numbers is assumed to be equal. -Example, temperature is an interval variable because the interval from one degree to the next is always the same Ratio variables are variables that meet the criteria for interval variables but also have meaningful zero points. (0mg of sugar or 0 children) Independent/Dependent/Confounding Variables - correct answers An independent variable has at least 2 levels that we either manipulate or observe to determine its effects on the dependent variable (amount of sugar consumed) A dependent variable is the outcome variable that we hypothesize to be related to or caused by the changes in the independent variable (activity level) A confounding variable is any variable that systematically varies with the independent variable so that we cannot logically determine which variable is at work; also called a confound Reliability & Validity - correct answers Reliability refers to the consistency of a measure Validity refers to the extent to which a test actually measures what it was intended to measure If researchers get drastically different results when they conduct the study a second time, the study would have low reliability The ACT is valid (and reliable) because it measures what a student learned in high school. However, tests that are reliable aren't always valid. For example, let's say your thermometer was a degree off. It would be reliable (giving you the same results each time) but not valid (because the thermometer wasn't recording the correct temperature). Hypothesis Testing - correct answers Process of drawing conclusions about whether a particular relation between variables is supported by the evidence Experiments & Correlations - correct answers Experiment- a study in which participants are randomly assigned to a condition of one or more independent variables to see if it effects the dependent variable Correlation- when random assignment is not possible (cannot assign gender or race), correlational research allows us to see how variables are related Frequency table - correct answers 1. Find highest and lowest score 2. Two columns: variable (# of volcanoes) and frequency (how many times 3. List range of values (include zero frequency values) 4. Count and list # of scores @ each value # of volcanoes | Frequency 17 | 2 16 | 0 15 | 0 14 | 1 Grouped frequency - correct answers # of volcanoes | Frequency 15-19 | 3 20-24 | 1 25-29 | 1 30-34 | 2 Histogram - correct answers Reports frequency of variable -variable on the x axis -frequency on the y axis -begin with zero on 0,0 point -draw bar for each value (centered over the value on the x axis Example: pacing indices Stem and leaf plot - correct answers Allows you to see all of the data points of variables numerically and visually Years of college education 1 | 0, 2, 4, 5, 8 2 | 2, 2, 3, 7 3 | 0 4 | 1, 3, 4, 5 1 | 0 = 10 Skewed distribution - correct answers Data not symmetrical, is skewed Positive skew - tail/mean to the right Floor effect - how many times a day you brush your teeth Negative skew - tail/mean to the left