Normal Distribution Flashcards
How do you calculate z score?
z = (x - mean) / standard deviation
When a normally distributed set of data is converted to Z scores what is it now known as?
The standard normal distribution
If a score has a p-value > 0.05 what can we conclude about its normalcy?
What if p < 0.05?
If your determined p-value is greater than 0.05 you can conclude that there is no reason to decide your results are not normal
If your p-value is < 0.05 you can conclude that the score/result is not normal
When trying to determine what score/result falls at a particular percentile what steops should you take?
(1) Determine the area between 0 and z
- for example we know that a z-score of 0 falls at the 50th percentile based on that we should be able to determine the area
(2) Go to the area table and determine the approximate value of z given the area between 0 and z
(3) Plug in all known data into the z-score formula and determine the value of X
What is Criterion Referencing?
This is the interpretation of a score based on its actual value
For Example: we need a 80% to pass this class (not based on classmates performance)
What is Norm Referencing?
This is the interpretation of a score based on its value relative to a standard or “normal score”
For Example: scores received on the NBE based on the standard
If a distribution is skewed to the left than it is _______.
Negatively skewed
If a distribution is skewed to the right than it is _______.
Positively Skewed
How do mean, median and mode fall on a negatively skewed and positively skewed curve?
Negative: Mean, Median, Mode
Positive: Mode, Median, Mean
What is the area under a bell curve?
1.0
What percentage of subjects (scores) fall within one standard deviation of the mean in a normal distribution?
68%
What percentage of subjects (scores) fall within two standard deviations of the mean in a normal distribution?
96%
What percentage of subjects (scores) fall within three standard deviation of the mean in a normal distribution?
99.7%
One Tailed Test
a statistical test in which the critical area of a distribution is one-sided so that it is either greater than or less than a certain value, but not both
If the sample that is being tested falls into the one-sided critical area which hypothesis will we reject and which one will we accept?
the alternative hypothesis will be accepted and the null hypothesis will be rejected
Type II Error (β)
This is a type of error that occurs when you accept a hypothesis that is false *False negative
Which type of statistical error is the most common?
Type I Error
What is the p value for a two tailed test?
P is approximately 0.25 or 25%
Two tailed test
a statistical test in which the critical area of a distribution is two sided and tests whether a sample is either greater than or less than a certain range of values
If the sample that is being tested falls into either of the critical areas which hypothesis will we reject and which one will we accept?
the alternative hypothesis will be accepted and the null hypothesis will be rejected
Type I Statistical Error (alpha)
This is a type of error that occurs when you reject a hypothesis that is true * aka False Positive
Based on the following:
A doctor believes that drug A is better than drug B in treating a disease.
What is the null and alternate hypotheses?
H₀: u₁ = u₂ OR H₀: u₁ ≤ u₂
H₁: u₁ ≠ u₂ OR H₁: u₁ > u₂
