In: Statistics and Probability
For this assignment, please submit the answers to the following questions, as well as an Excel spreadsheet which documents the work you did.
Do poets die young? According to William Butler Yeats, “She is the Gaelic muse, for she gives inspiration to those she persecutes. The Gaelic poets die young, for she is restless, and will not let them remain long on earth.” One study designed to investigate this issue examined the age at death for writers from different cultures and genders. Three categories of writers examined were novelists, poets, and nonfiction writers. The ages at death for female writers in these categories from North America are given in the dataset on blackboard (data file : Female Writers.xls). Most of the writers are from the United States, but Canadian and Mexican writers are also included.
a) Use Excel to build a boxplot of the three
associated data sets. If the population mean death ages were the
same for the three populations, would you expect to see a boxplot
like this? Please elaborate.
b) Write down both the null and alternative hypothesis
for the one-way ANOVA.
c) Run the one-way ANOVA test in Excel; make sure you save this in your spreadsheet somewhere where it can be found.
d) You will see a value for F-stat. Report this value, and explain how it is related to MSA and MSW.
e) In general, what is a p-value? In your table, what p-value is reported, and what exactly does it mean?
f) At the .05 level of significance, is there evidence of a difference in mean age of death among the various types of female writers? Explain your decision.
Novels | Poems | Nonfiction |
57 | 88 | 74 |
90 | 69 | 86 |
67 | 78 | 87 |
56 | 68 | 68 |
90 | 72 | 76 |
72 | 60 | 73 |
56 | 50 | 63 |
90 | 47 | 78 |
80 | 74 | 83 |
74 | 36 | 86 |
73 | 87 | 40 |
86 | 55 | 75 |
53 | 68 | 90 |
72 | 75 | 47 |
86 | 78 | 91 |
82 | 85 | 94 |
74 | 69 | 61 |
60 | 38 | 83 |
79 | 58 | 75 |
80 | 51 | 89 |
79 | 72 | 77 |
77 | 58 | 86 |
64 | 84 | 66 |
72 | 30 | 97 |
88 | 79 | |
75 | 90 | |
79 | 66 | |
74 | 45 | |
85 | 70 | |
71 | 48 | |
78 | 31 | |
57 | 43 | |
54 | ||
50 | ||
59 | ||
72 | ||
60 | ||
77 | ||
50 | ||
49 | ||
73 | ||
39 | ||
73 | ||
61 | ||
90 | ||
77 | ||
57 | ||
72 | ||
82 | ||
54 | ||
62 | ||
74 | ||
65 | ||
83 | ||
86 | ||
73 | ||
79 | ||
63 | ||
72 | ||
85 | ||
91 | ||
77 | ||
66 | ||
75 | ||
90 | ||
35 | ||
86 |
a) Boxplot:
1) Boxplot for novels:
here Q1=61 ;Median=73; Q3=80; IQ range=19; N=67 No outlier in this data
2) Boxplot for poems:
here Q1=48.5 ; Median=68: Q3=77.25; IQ range=28.75,N=32 No outlier
3) Boxplot for Nonfiction
here Q1= 69.25; Median=77.5 ; Q3=86.75 ; IQ range= 17.5; N=24
there is one outlier=40
A)
Hypothesis:
Null hypothesis: H0:
Alternative hypothesis:H1: Not H0
Test statistics:
F=MSG/MSE
Decision rule:
Reject H0 if F> F(n-1)(n-k)0.05
Hypothesis testing using MS-excel:
Anova: Single Factor | ||||||
SUMMARY | ||||||
Groups | Count | Sum | Average | Variance | ||
Novels | 67 | 4787 | 71.44776 | 170.3419 | ||
Poems | 32 | 2022 | 63.1875 | 299.1895 | ||
Nonfiction | 24 | 1845 | 76.875 | 198.7228 | ||
ANOVA | ||||||
Source of Variation | SS | df | MS | F | P-value | F crit |
Between Groups | 2744.193 | 2 | 1372.096 | 6.562944 | 0.001973 | 3.071779 |
Within Groups | 25088.07 | 120 | 209.0672 | |||
Total | 27832.26 | 122 |
Conclusion:
here F value 6.5629>3.0717 also here p-value 0.0019<0.05 so we reject H0 and conclude that there is a statistically significant difference between these three groups( Novel, poems, and nonfiction)