Chapter 1
A researcher conducts an experiment to determine whether different doses of an over-the-counter supplement, St. John’s Wort, have any effect of memory for college students. What type of variable is St. John's Wort?
What is an independent variable?
St. John's Wort is the variable we are manipulating in order to see its impact on memory (dependent variable).
For the following frequency distribution, how many individuals had a score of X = 2?
X f
5 2
4 4
3 1
2 3
What is 3?
If a set of exam scores forms a symmetrical distribution, what percentage of the students’ scores with be above and below the mean?
What is 50%?
Rember, the mean is the balancing point in the data set so if the distribution is symmetrical or normal then the mean falls right in the middle of the graph.
The distance from one score to another tends to increase, and a single score tends to provide a less accurate representation of the entire distribution when this quantitative measurement increases.
What is variability?
A sample of n=10 scores has a M=5. One person with a score of X=16 is added to the distribution. What is the mean for the new set of scores?
M=11
We know the sum of scores if 10x5=50, then we add in the 16=66, and we divide by the new sample size 66/11=11=the new mean.
T/F: A data set is described as consisting of n= 15 scores. Based on the notation being used, the data set is a sample.
What is true?
n=sample
N=population
A researcher measures eye color for a sample of n= 50 people. Which measure of central tendency would be appropriate to summarize the measurements?
What is mode?
A population with a mean of μ = 6 has ΣX = 54. How many scores are in the population?
What is 9?
54/6=9
Variance is represented by what notation?
Sigma squared (σ2)
What is the name for the natural difference, that occurs by chance, between a statistic and a parameter?
What is a sampling error?
A bar graph is appropriate for scores measured on what level/scale of measurement?
What is nominal?
What is the range of x?
X f
6 1
5 2
4 2
3 3
2 5
1 2
What is 5?
6 (greatest score)-1(smallest score)=5
When you add the deviations and compute taveragereg, what sum do you always get?
What is 0?
Because the deviation is the difference between a score and the mean, and we know the mean acts as a balancing point, there must be equal distances on both sides of the mean.
What additional information is obtained by measuring on an interval scale compared to an ordinal scale?
What is the size/magnitude of the differences (i.e. width)?
Ordinal (1st, 2nd, 3rd, etc) gives an ordered sequence while interval tells us the size or magnitude between observations.
The following formula is the way to find what common measure in frequency distribution?
p=f/n
What is the proportion?
This is the formula for what statistical measure?
μ=ΣX/N
What is populaiton mean?
All the possible samples of n=3 are selected from a population with μ = 30 and σ = 5 and the mean is computed for each of the samples. If the value obtained is 30, this is an example a biased or unbiased statistic?
What is unbiased?
It is unbiased becasue the average value (mean) of the statistic is equal to the population statistic (population mean).