Inference flashcards
34 practice cards drawn from the Inference lessons. Tap a card to turn it over. Every answer is checked against the lesson it came from.
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What is an estimator that is right on average across many samples called?
unbiased
from “Point Estimates”
What is an estimator that is always exactly correct called?
impossible
from “Point Estimates”
For an unbiased sample variance from 19 readings, what do you divide by?
18
from “Unbiased Sample Variance”
For an unbiased sample variance from 25 readings, what do you divide by?
24
from “Unbiased Sample Variance”
Which hypothesis is "the mean is unchanged"?
from “Null and Alternative Hypotheses”
Which hypothesis is "the new drug works better"?
from “Null and Alternative Hypotheses”
At 5 percent, what is the critical z for a one-tailed test?
1.645
from “One-Tailed and Two-Tailed”
At 5 percent, what is the critical z for a two-tailed test?
1.96
from “One-Tailed and Two-Tailed”
The claimed mean is 67, sigma is 10, n = 4, and the sample mean is 77. What is z?
2
from “The Z-Test”
The claimed mean is 84, sigma is 20, n = 25, and the sample mean is 80. What is z?
-1
from “The Z-Test”
The test is one-tailed at 5 percent and the statistic is 1.2. What do you conclude?
do not reject
from “Critical Regions”
The test is one-tailed at 5 percent and the statistic is 0.5. What do you conclude?
do not reject
from “Critical Regions”
A test of the claim that a new mug keeps coffee hot longer gives p = 0.02. Which conclusion is best?
evidence the mug keeps coffee hot longer
from “P-Values”
p = 0.3 at the 5 percent level. What do you conclude?
do not reject
from “P-Values”
The tail comes to p = 0.01. Which conclusion is best?
evidence the die favors sixes
from “Testing a Proportion with the Binomial”
The tail comes to p = 0.004. Which conclusion is best?
evidence the die favors sixes
from “Testing a Proportion with the Binomial”
What kind of error is failing to reject a false ?
type two
from “Type One and Type Two Errors”
What kind of error is rejecting a true ?
type one
from “Type One and Type Two Errors”
The sample mean is 56 and the standard error is 1. What is the 95 percent interval?
from “Confidence Intervals”
The sample mean is 78 and the standard error is 5. What is the 95 percent interval?
from “Confidence Intervals”
What count would the marked cell hold if home and pet were unlinked?
30
from “Expected Frequencies”
What does an expected frequency describe?
the count if the two categories were unlinked
from “Expected Frequencies”
χ² comes to 5.6 against a critical value of 3.84. What do you conclude?
reject : the two are linked
from “The Chi-Squared Test for Independence”
χ² comes to 1.2 against a critical value of 3.84. What do you conclude?
do not reject : no evidence of a link
from “The Chi-Squared Test for Independence”
A goodness of fit test uses 5 categories. How many degrees of freedom?
4
from “The Chi-Squared Goodness of Fit Test”
χ² = 7.2 with a critical value of 11.07. What is the conclusion?
no evidence the die is unfair
from “The Chi-Squared Goodness of Fit Test”
There is one sample of 8, one claimed mean, and the population spread is unknown. Which test applies?
a one-sample t-test
from “The One-Sample T-Test”
|t| = 1.14 against a critical value of 2.2. What do you conclude?
no evidence the mean differs from 500 ml
from “The One-Sample T-Test”
Two independent samples are taken and the population spread is unknown. Which test compares the means?
a two-sample t-test
from “The Two-Sample T-Test”
The t-test returns p = 0.03 at the 5 percent level. What do you conclude?
evidence the means differ
from “The Two-Sample T-Test”
n = 21, , and claims . What is the statistic?
40
from “Testing a Variance with Chi-Squared”
The statistic is 19.8 against an upper critical value of 23.68. What follows?
no evidence the spread exceeds the claim
from “Testing a Variance with Chi-Squared”
F comes to 4.2 against a critical value of 3.68. What do you conclude?
evidence the two spreads differ
from “Comparing Two Variances with the F-Test”
F comes to 3.1 against a critical value of 3.68. What do you conclude?
no evidence the two spreads differ
from “Comparing Two Variances with the F-Test”