z-score Basics
What does it mean if a z-score is 0?
The data value is the mean.
What is the probability of an event that will NEVER occur?
0 or 0%
In recent years, it was found that teenagers between ages 13 - 17 send/receive an average of 1740 text messages per month with a standard deviation of 550 text messages.
What is the z-score for a teenager who sends/receives 2150 text messages per month?
0.745
What does it mean if a z-score is positive?
The data value is above the mean.
What is the probability of an event that is CERTAIN to occur?
1 or 100%
In recent years, it was found that teenagers between ages 13 - 17 send/receive an average of 1740 text messages per month with a standard deviation of 550 text messages.
If a teenager has a z-score of 1.38, about how many text messages did he or she send/receive that month?
2499
What does it mean if a z-score is negative?
The data value is below the mean.
How many sides are on a coin?
2
The Virginia Cooperative Extension reports that the mean weight of yearling (1-yo) Angus cattle is 1150 lbs. with a standard deviation of 80 lbs.
What is the z-score for a cow weighing 980 lbs.?
-2.125
Define z-score in your own words.
A z-score represents the number of standard deviations a data value is away from the mean.
How many sides are on one standard die?
6
The Virginia Cooperative Extension reports that the mean weight of yearling (1-yo) Angus cattle is 1150 lbs. with a standard deviation of 80 lbs.
Is a cow weighing 1340 unusual? Explain.
Yes. The z-score is more than 2 s.d. from the mean.
Give the formula for calculating a z-score.
z = (x - mean) / sd
How many cards are in a standard deck (excluding Jokers)?
52
x = (z)(s.d.) + mean