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
There are 16 students in Mike's math class. One person is to be randomly chosen to write the homework on the board. What is the probability that Mike will be chosen?
1/16 or 6.25%
Is probability tested on the ACT?
Yes!
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
Consider the contingency table provided by your host. What is the probability that a randomly chosen student is a male business student?
1/4 or 25%
Statistics & Probability is approximately ____% of the ACT Math test.
(any response 8 - 12)
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
Consider the contingency table provided by your host. What is the probability that a randomly chosen female student is enrolled in Technology?
5/30 or 1/6 or 16.7%
Give an equation of the line thru (-2, 4) & (2, -1)
y = (-5/4)x + 3/2
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.
A spinner has sections numbered: 1, 1, 3, 3, 5. A cube has sides numbered 1 - 6 (one time each). What is the probability that the spinner AND number cube will both land on 1?
1/15
Give the formula for average rate of change.
m = (y2 - y1)/(x2 - x1) a.k.a. slope formula
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
Consider the contingency table provided by your host. What is the probability that a randomly chosen Technology student is female?
5/50 or 1/10 or 10%
Consider the contingency table provided by your host. What is the probability that a randomly chosen student is a male or in Business?
95/100 or 95%