# Statistics Cheat Sheet

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What proportion of a normal distribution is located in the tail beyond z = +2.00?
0.0228
What proportion of a normal distribution is located between the mean and z = 1.40?
0.4192
The Z-score corresponding to the 52nd percentile is
.05
A normally distributed variable has a mean of 10 and a standard deviation of 2. The probability that a value between 7 and 9 is obtained is
.2417
An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life for a particular use before they failed is 19.0 hours. The distribution of the lives approximated a normal distribution. The standard deviation was 1.2 hours. About 95.44% of the batteries failed between what two values?
16.6 & 21.4
The average time students need
n = 100 with s^2 = 100
I other factors are held constant, which set of characteristics is most likely to produce a significant t statistic? n = 50 with s^2 = 50
If other factors are held constant, what is the effect of increasing the sample size?
It will decrease the estimated standard error and increase the likelihood of rejecting H0
A researcher conducts a one-sample hypothesis test using a sample of n = 40 from an unknown population. What is the df value for the t statistic?
39
With α= 0.05, what is the critical t value for a one-tailed test with n = 15? t = 1.761 With α= 0.05 and df = 20, the critical values for a two-tailed t test are t = +-2.086. Assuming all other factors are held constant, if the df value were decreased to df = 10, what would happen to the critical values for t?
They would increase (move farther from zero).
A sample of n = 4 scores is selected from a population with an unknown mean. The sample has a mean of M = 40 and a variance of s2= 16. Which of the following is the correct 90% confidence interval for μ? μ= 40 +-2.353(2)
When is it appropriate to use the two sample, pooled variance t-test? When
2 independent samples are compared.
Which of the following accurately describes an independent-measures study?
It uses a different group of participants for each of the treatment conditions being compared.
Which of the following is the correct null hypothesis for an independent-measures t test?
Mu1-Mu2 = 0 Accounting procedures allow a