The Basics
What is the difference between descriptive and inferential statistics?
Descriptive statistics are used to organize, summarize, and make sense of data.
Inferential statistics are used to infer or generalize observations made with samples tot he larger population.
When should one display ungrouped data?
nominal/qualitative data
What are the 3 measures of central tendency?
mean, median, mode
In what situations can variability be a negative number?
Never
What are three commonly used research methods in the behavioral sciences?
Experiments, quasi-experiments, and correlational designs
What is one of the rules when creating a simple frequency distribution?
1. Defined intervals
2. Equidistant intervals
3. No overlapping intervals
4. Values rounded to the same degree of accuracy as original data
When is the mean the best measure of central tendency? (Hint: must mention scale of measurement AND type of distribution)
interval/ratio scale data
normal distribution
Based on the empirical rule, we know that what proportion of data are within 2 SD of the mean?
95%
A researcher samples 100 college students for their study and finds that on average, students who take public transportation sleep less than 7 hours a night. Is the "7 hours a night" a parameter or statistic?
a sample statistic
When would you use a bar chart instead of a histogram?
Discrete data
What is the only measure of central tendency that can be used with nominal data?
Mode
If the sample size increases, how will this affect the variance?
A researcher examined how effective different types of soil were by counting the the number of new leaves sprouted. What scale of measurement did the researcher use to measure the outcome variable?
Ratio scale
Out of a sample of 20 students, 3 reported that statistics was their favorite class. What is the relative percentage of those who reported statistics as their favorite class?
15%
When would you use the median as the best measure of central tendency?
Ordinal data OR
Skewed distribution with interval/ratio data
The researcher computes a SS of 1000 with a sample size of 11. What is the sample standard deviation?
1000/(11-1) = 100
sqrt(100) = 10
A study is conducted to examine whether the number of aggressive behaviors by individuals varies by the region in which participants grew up (northern vs. southern U.S. states). Is the predictor variable an independent variable or a quasi-independent variable?
Quasi-independent variable
(60-6) + 1 = 55
55 / 5 = 11
When will the weighted mean be equal to the arithmetic mean?
Calculate the SS for the following data:
3, 4, 5, 6, 7
10