{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

CH11 exercises solutions

CH11 exercises solutions - X X X X X X X X X X X X X X X X...

This preview shows pages 1–4. Sign up to view the full content.

X X X X X X X X X X X X X X X X AP Statistics Packet 11 X Inference for Distributions Inference for the Mean of a Population Comparing Two Means X X X X X X

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
HW #19 1 – 4, 7 - 10 11.1 Writers in some fields often summarize data by giving x and its standard error rather than x and s. The standard error of the mean x is often abbreviated as SEM. (a) A medical study finds that x = 114.9 and s = 9.3 for the seated systolic blood pressure of the 27 members of one treatment group. What is the standard error of the mean? 1.7898 s n 9.3 = = 27 (b) Biologists studying the levels of several compounds in shrimp embryos reported their results in a table, with the note, “Values are means ± SEM for three independent samples.” The table entry for the compound ATP was 0.84 ± 0.01. The researchers made three measurements of ATP, which had x = 0.84. What was the sample standard deviation s for these measurements? Since 0.01 , 0.0173 3 s s = = 11.2 What critical value t * from Table C satisfies each of the following conditions? (a) The t distribution with 5 degrees of freedom has probability 0.05 to the right of t * . 2.015 (invT (.95, 5)) (b) The t distribution with 21 degrees of freedom has probability 0.99 to the left of t * . 2.518 (invT (.99, 21)) 11.3 What critical value t * from Table C satisfies each of the following conditions? (a) The one-sample t statistic from a sample of 15 observations has probability 0.025 to the right of t * . 2.145 (invT (.975, 14)) (b) The one-sample t statistic from an SRS of 20 observations has probability 0.75 to the left of t * . 0.688 (invT (.75, 19)) 11.4 What critical value t * from Table C should be used for a confidence interval for the mean of the population in each of the following situations? (a) A 90% confidence interval based on n = 12 observations. df = 11, t * = 1.796 (a) A 95% confidence interval from an SRS of 30 observations. df = 29, t * = 2.045 (a) An 80% confidence interval from a sample of size 18. df = 17, t * = 1.333
11.7 The one-sample t statistic for testing 0 :0 A H H m m = from a sample of n = 15 observations has the value t = 1.82. (a) What are the degrees of freedom for this statistic? df = 14 (b) Give the two critical values t * from Table C that bracket t. What are the right-tail probabilities p for these two values? 1.82 is between 1.761 ( p = 0.05) and 2.145 ( p = 0.025). (c) Between what two values does the P- value of the test fall? The P- value is between 0.025 and 0.05 (in fact, p = tcdf( 1.92, , 14) = 0.0451). (d) Is the value t = 1.82 statistically significant at the 5% level? At the 1% level? t = 1.82 is significant at α = 0.05 but not at α = 0.01. 11.8 The one-sample t statistic from a sample of n = 25 observations for the two-sided test of 0 : : A H H m m = 64 ≠ 64 has the value t = 1.12. , (a) What are the degrees of freedom for this statistic? df = 24 (b) Give the two critical values t * from Table C that bracket t. What are the right-tail probabilities p for these two values? 1.12 is between 1.059 ( p = 0.15) and 1.318 ( p = 0.10). (c) Between what two values does the P- value of the test fall? (Note that A H is two-sided.) The P- value is between 0.30 and 0.20 (in fact, p = 2tcdf( 1.12, , 24) = 0.2738).

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 22

CH11 exercises solutions - X X X X X X X X X X X X X X X X...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online