SESN+8+ASSIGN-2

Fall 2014-SESSION 8 LECTURE and ASSIGNMENTS-２

問題

Scenario A You want to know if your students do better learning using film or traditional lecture and discussion activities in social studies class. You want to try both methods with the students and compare the results. Which design would you use and how you would organize the study showing the assessment points. This is a repeated measures posttest design (no pretest so we don’t use gain scores). The data in the chart below provides the scores of the sample in the study.

.
 * || Traditional || Film ||  ||   ||
 * 1.male || 78 || 82 ||  ||   ||
 * 2.male || 83 || 90 ||  ||   ||
 * 3.male || 96 || 100 ||  ||   ||
 * 4.male || 80 || 80 ||  ||   ||
 * 5.male || 79 || 82 ||  ||   ||
 * 6.male || 100 || 95 ||  ||   ||
 * 7.male || 75 || 87 ||  ||   ||
 * 8.male || 88 || 93 ||  ||   ||
 * 9.male || 82 || 84 ||  ||   ||
 * 10.female || 88 || 85 ||  ||   ||
 * 11.female || 97 || 95 ||  ||   ||
 * 12. female || 95 || 79 ||  ||   ||
 * 13.female || 91 || 85 ||  ||   ||
 * 14.female || 80 || 85 ||  ||   ||
 * 15.female || 78 || 78 ||  ||   ||
 * 16.female || 83 || 81 ||  ||   ||
 * 17.female || 97 || 90 ||  ||   ||
 * 18.female || 99 || 90 ||  ||   ||
 * 19.female || 90 || 92 ||  ||   ||
 * Average or mean for class under each condition ||  ||   ||   ||   ||
 * Standard Deviation ||  ||   ||   ||   ||

数字入れたら、出てきた. http://graphpad.com/quickcalcs/ttest1/?Format=C

Paired //t// test results
The two-tailed P value equals 0.8340 By conventional criteria, this difference is considered to be not statistically significant.
 * **P value and statistical significance:**

The mean of Traditional lecture minus Film equals 0.32 95% confidence interval of this difference: From -2.80 to 3.44
 * Confidence interval:**

t = 0.2127 df = 18 standard error of difference = 1.485
 * Intermediate values used in calculations:**

GraphPad's web site includes portions of the manual for GraphPad Prism that can help you learn statistics. First, review the meaning of [|P values] and [|confidence intervals]. Then learn how to interpret results from an [| unpaired] or [|paired]//t// test. These links include GraphPad's popular //analysis checklists//.
 * Learn more:**


 * Review your data:** ||


 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

=ーー　ここから、我々の答え　ーー=

Using "Paired //t// test results",
the standard deviation (SD) the standard error of the mean (SEM)
 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

Which treatment has the higher average? Traditional Which time were the scores more homogenous (range smaller and group tighter)? Film The standard deviation will tell you this. . Next session we will discuss more about these data including what the t-test showed. But for now just answer these questions: In the Traditional condition: Mean = 87.32 SD = 8.19 SEM = 1.88 Which students scored more than 2 deviations from the mean? (below and above)
 * 87.32+8.19x2 = 103.7 --> students # none
 * 87.32-8.19x2 = 70.94 --> students # none

Which student fell in within 2 points of the 50th percentile? 85.32 ~89.32 == # 8, 10 (88) . In the Film condition: Mean = 87.00 SD = 6.17 SEM = 1.42 Which students scored more than 2 deviations from the mean? Which student fell in within 2 points of the 50th percentile? 85.00 ~ 89.00 == #7, 10, 13, 14
 * 87.32+2 = 89.32
 * 87.32-2= 85.32
 * 87.00+6.17x2 = 99.34 --> students #3
 * 87.00-6.17x2 = 74.66 --> students # none
 * 87.00+2 = 89.00
 * 87.00-2 = 85.00

__//**Do you have any hypotheses about these scores?**//__ - It seems that there is no significant statistical differences between traditional and film treatments to this group. However we have noticed that there are 9 males and 10 females in the examples. We checked their averages then we found that male students responded positively to the film treatment but female responded just the opposite as we added below. This shows that this treatments have different effect to gender differences.

We checked the average for each gender.
 * || tradition average || film average ||
 * male -- 9 students || 84.55 || 88.11 ||
 * female -- 10 students || 89.8 || 86.0 ||

=ーー　答え　終了ーー=

Fall 2014-SESSION 8 LECTURE and ASSIGNMENTS-3

下の方. ..

Let’s see if you can make some sense of descriptive statistics by revisiting this scenario. Scenario A You want to know if your students do better learning using film or traditional lecture and discussion activities in social studies class. You want to try both methods with the students and compare the results. Which design would you use and how you would organize the study showing the assessment points. This is a repeated measures posttest design (no pretest so we don’t use gain scores). The data in the chart below provides the scores of the sample in the study.

.
 * || Traditional || Film ||  ||   ||
 * 1.male || 78 || 82 ||  ||   ||
 * 2.male || 83 || 90 ||  ||   ||
 * 3.male || 96 || 100 ||  ||   ||
 * 4.male || 80 || 80 ||  ||   ||
 * 5.male || 79 || 82 ||  ||   ||
 * 6.male || 100 || 95 ||  ||   ||
 * 7.male || 75 || 87 ||  ||   ||
 * 8.male || 88 || 93 ||  ||   ||
 * 9.male || 82 || 84 ||  ||   ||
 * 10.female || 88 || 85 ||  ||   ||
 * 11.female || 97 || 95 ||  ||   ||
 * 12. female || 95 || 79 ||  ||   ||
 * 13.female || 91 || 85 ||  ||   ||
 * 14.female || 80 || 85 ||  ||   ||
 * 15.female || 78 || 78 ||  ||   ||
 * 16.female || 83 || 81 ||  ||   ||
 * 17.female || 97 || 90 ||  ||   ||
 * 18.female || 99 || 90 ||  ||   ||
 * 19.female || 90 || 92 ||  ||   ||
 * Average or mean for class under each condition ||  ||   ||   ||   ||
 * Standard Deviation ||  ||   ||   ||   ||

=
===============.
 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

http://graphpad.com/quickcalcs/ttest1/?Format=C

Paired //t// test results
The two-tailed P value equals 0.8340 By conventional criteria, this difference is considered to be not statistically significant.
 * **P value and statistical significance:**

The mean of Traditional lecture minus Film equals 0.32 95% confidence interval of this difference: From -2.80 to 3.44
 * Confidence interval:**

t = 0.2127 df = 18 standard error of difference = 1.485
 * Intermediate values used in calculations:**

GraphPad's web site includes portions of the manual for GraphPad Prism that can help you learn statistics. First, review the meaning of [|P values] and [|confidence intervals]. Then learn how to interpret results from an [| unpaired] or [|paired]//t// test. These links include GraphPad's popular //analysis checklists//.
 * Learn more:**


 * Review your data:** ||


 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

====

.

.
 * || Traditional || Film ||  ||   ||
 * 1.male || 78 || 82 ||  ||   ||
 * 2.male || 83 || 90 ||  ||   ||
 * 3.male || 96 || **__ 100 __** ||  ||   ||
 * 4.male || 80 || 80 ||  ||   ||
 * 5.male || 79 || 82 ||  ||   ||
 * 6.male || 100 || 95 ||  ||   ||
 * 7.male || 75 || 87 ||  ||   ||
 * 8.male || 88 || 93 ||  ||   ||
 * 9.male || 82 || 84 ||  ||   ||
 * 10.female || 88 || 85 ||  ||   ||
 * 11.female || 97 || 95 ||  ||   ||
 * 12. female || 95 || 79 ||  ||   ||
 * 13.female || 91 || 85 ||  ||   ||
 * 14.female || 80 || 85 ||  ||   ||
 * 15.female || 78 || 78 ||  ||   ||
 * 16.female || 83 || 81 ||  ||   ||
 * 17.female || 97 || 90 ||  ||   ||
 * 18.female || 99 || 90 ||  ||   ||
 * 19.female || 90 || 92 ||  ||   ||
 * Average or mean for class under each condition ||  ||   ||   ||   ||
 * Standard Deviation ||  ||   ||   ||   ||

.


 * Standard Deviation and Standard Error of the Mean
 * Key concepts: SD
 * Computing the SD
 * How accurately does a SD quantify scatter?
 * Key concepts: SEM
 * Computing the SEM
 * The SD and SEM are not the same
 * Advice: When to plot SD vs. SEM
 * Alternatives to showing the SD or SEM

http://www.graphpad.com/guides/prism/6/statistics/index.htm?stat_semandsdnotsame.htm

=The SD and SEM are not the same = It is easy to be confused about the difference between the standard deviation (SD) and the standard error of the mean (SEM). Here are the key differences: • The SD quantifies scatter — how much the values vary from one another. •  The SEM quantifies how precisely you know the true mean of the population. It takes into account both the value of the SD and the sample size. • Both SD and SEM are in the same units -- the units of the data. •  The SEM, by definition, is always smaller than the SD. • The SEM gets smaller as your samples get larger. This makes sense, because the mean of a large sample is likely to be closer to the true population mean than is the mean of a small sample. With a huge sample, you'll know the value of the mean with a lot of precision even if the data are very scattered. • The SD does not change predictably as you acquire more data. The SD you compute from a sample is the best possible estimate of the SD of the overall population. As you collect more data, you'll assess the SD of the population with more precision. But you can't predict whether the SD from a larger sample will be bigger or smaller than the SD from a small sample. (This is not strictly true. It is the variance -- the SD squared -- that doesn't change predictably, but the change in SD is trivial and much much smaller than the change in the SEM.) <span class="f_BodyText">Note that standard errors can be computed for almost any parameter you compute from data, not just the mean. The phrase "the standard error" is a bit ambiguous. The points above refer only to the standard error of the mean.
 * URL of this page:** @http://www.graphpad.com/guides/prism/6/statistics/index.htm?stat_semandsdnotsame.htm

http://graphpad.com/guides/prism/6/statistics/index.htm?stat_qa_choosing_a_test_to_compare_.htm

=<span class="f_Heading1">Q&A: Choosing a test to compare two groups =

<span class="f_Heading3">If I have data from three or more groups, is it OK to compare two groups at a time with a t test?
<span class="f_BodyText">No. You should analyze all the groups at once with [|one-way ANOVA], and then follow up with [|multiple comparison tests]. The only exception is when some of the 'groups' are really controls to prove the assay worked, and are not really part of the experimental question you are asking.

<span class="f_Heading3">I know the mean, SD (or SEM) and sample size for each group. Which tests can I run?
<span class="f_BodyText">You can [|enter data] as mean, SD (or SEM) and N, and Prism can compute an unpaired t test. Prism cannot perform an paired test, as that requires analyzing each pair. It also cannot do any nonparametric tests, as these require ranking the data.

<span class="f_Heading3">I only know the two group means, and don't have the raw data and don't know their SD or SEM. Can I run a t test?
<span class="f_BodyText">No. The t test compares the difference between two means and compares that difference to the standard error of the difference, computed from the standard deviations and sample size. If you only know the two means, there is no possible way to do any statistical comparison.

<span class="f_Heading3">Can I use a normality test to make the choice of when to use a nonparametric test?
<span class="f_BodyText">It is [|not a good idea] to base your decision solely on the normality test. Choosing when to use a nonparametric test is not a straightforward decision, and you can't really automate the process.

<span class="f_Heading3">I want to compare two groups. The outcome has two possibilities, and I know the fraction of each possible outcome in each group. How can I compare the groups?
<span class="f_BodyText">Not with a t test. Enter your data into a [|contingency table] and analyze with [|Fisher's] exact test.

<span class="f_Heading3">I want to compare the mean survival time in two groups. But some subjects are still alive so I don't know how long they will live. How can I do a t test on survival times?
<span class="f_BodyText">You should use special methods designed to [|compare survival curves]. Don't run a t test on survival times.

<span class="f_Heading3">I don't know whether it is ok to assume equal variances. Can't a statistical test tell me whether or not to use the Welch t test?
<span class="f_BodyText">While that sounds like a good idea, in fact it is not. The decision really should be made as part of the experimental design and not based on inspecting the data.

<span class="f_Heading3">I don't know whether it is better to use the regular paired t test or the ratio test. Is it ok to run both, and report the results with the smallest P value?
<span class="f_BodyText">No. The results of any statistical test can only be interpreted at face value when the choice of analysis method was part of the experimental design.
 * URL of this page:** @http://graphpad.com/guides/prism/6/statistics/index.htm?stat_qa_choosing_a_test_to_compare_.htm

Unpaired //t// test results
The two-tailed P value equals 0.8940 By conventional criteria, this difference is considered to be not statistically significant.
 * **P value and statistical significance:**

The mean of Traditional lecture minus Film equals 0.32 95% confidence interval of this difference: From -4.46 to 5.09
 * Confidence interval:**

t = 0.1342 df = 36 standard error of difference = 2.353
 * Intermediate values used in calculations:**

GraphPad's web site includes portions of the manual for GraphPad Prism that can help you learn statistics. First, review the meaning of [|P values] and [|confidence intervals]. Then learn how to interpret results from an [| unpaired] or [|paired]//t// test. These links include GraphPad's popular //analysis checklists//.
 * Learn more:**


 * Review your data:** ||


 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

Welch //t// test results
The two-tailed P value equals 0.8941 By conventional criteria, this difference is considered to be not statistically significant.
 * **P value and statistical significance:**

The mean of Traditional lecture minus Film equals 0.32 95% confidence interval of this difference: From -4.47 to 5.10
 * Confidence interval:**

t = 0.1342 df = 33 standard error of difference = 2.353
 * Intermediate values used in calculations:**

GraphPad's web site includes portions of the manual for GraphPad Prism that can help you learn statistics. First, review the meaning of [|P values] and [|confidence intervals]. Then learn how to interpret results from an [| unpaired] or [|paired]//t// test. These links include GraphPad's popular //analysis checklists//.
 * Learn more:**


 * Review your data:** ||


 * ~ Group ||~ Traditional lecture ||~ Film ||
 * Mean || 87.32 || 87.00 ||
 * SD || 8.19 || 6.17 ||
 * SEM || 1.88 || 1.42 ||
 * N || 19 || 19 ||

Traditional lecture 78 83 96 80 79 100 75 88 82 88 97 95 91 80 78 83 97 99 90

- Film 82 90 100 80 82 95 87 93 84 85 95 79 85 85 78 81 90 90 92

.