Exam 2 Flashcards
(42 cards)
Describe how a stem-and-leaf plot provides a graphic representation of data.
The leaf portion of the plot consists of the last single digit of the score, and the
stem consists of the rest of the leftmost digits.
Describe what a normal distribution is.
A normal distribution is a distribution that follows a bell-shaped curve.
Meaning that the majority of scores fall in the middle of the distribution, with less on either extreme end of the distribution.
What is mode?
the score that appears most frequently in a distribution
What is median?
the value that is perfectly in the middle of a distribution when the values are listed numerically
What is mean?
the sum of a set of scores divided by the number of scores (resulting in the average score)
What is range?
the difference between the highest and lowest values in a distribution
What is variance?
it indicates how close together or far apart points of data are in relation to each other (low variance = scores are close together)
What is coefficient of variation?
a measure of variability that can be used to describe data measured on the interval or ratio scale
What is sampling error?
the tendency for sample values to differ from population values
What do percentiles mean?
percentiles help us describe a score’s position within a distribution. scoring in the 90th percentile means that that individual’s score is higher than 90% of scores. a 50th percentile score is the median
What does the z-score mean?
we use z-score to describe how many standard deviations away a score is
-2 = 2 standard deviations below the mean (below average
-1 = 1 standard deviation below the mean
0 = the mean (average, 50th percentile-ish)
1 = 1 standard deviation above the mean
2 = 2 standard deviations above the mean (above average)
What is σX̅ ?
the standard error of the mean which is an estimate of the population standard deviation
What is sX̅?
the standard deviation and size of the sample
What is a confidence interval?
It is a range of scores with specific boundaries that are highly likely to contain the population mean
How is a t-distribution different from a standard normal distribution?
the t distribution is used to evaluate small samples, rather than the standard normal distribution that evaluates a full population
Define Null Hypothesis
the null hypothesis is a hypothesis that states that the observed outcome was solely due to chance or error (group means are not different)
Define Null Hypothesis
the null hypothesis is a hypothesis that states that the observed outcome was solely due to chance or error (group means are not different)
How is “degrees of freedom” used to specify the t-distribution?
it is used instead of n. it represents n-1
What is a Type 1 error?
When you reject the null hypothesis when the null hypothesis is actually true.
What is a Type 2 error?
When you DO NOT reject the null hypothesis when it is actually false.
What is statistical power?
the probability that a test will lead to the rejection of the null hypothesis
If an individual scores 2 standard deviations above the mean on a standardized test, what is their z-score?
z = 2
If an individual scores 2 standard deviations above the mean on a standardized test, what is their z-score?
z = 2
How does adjusting alpha affect the likelihood of committing a Type 1 error?
The higher alpha is, the more likely it is to commit a type 1 error. Example: if alpha = 0.05 there is a 5% chance of committing a type 1 error (this is an accepted minimal risk)
