Friday, September 13, 2019

Notes for Homework 4, due September 16

Notes on contingency tables

In Excel: the sum of a row will be of the form
=sum(a1:c1) where the letters are the changing indices

The sum of a column will be
=sum(a1:a5) where the numbers are the changing indices

Notes on the Central Limit Theorem

In Excel: In my version of Excel, the function that gives you the proportion less than a z-score is

=norm.dist(x, mean, standard_dev, cumulative)

The cumulative value should be 1 always.

If we are doing a Central Limit z-score based on the average of a sample, the instruction is changed as follows. 

=norm.dist(x, mean, standard_dev/sqrt(n), cumulative)

where n is the size of the sample.

Notes on probabilities of independent trials

In Excel: Again, different versions of Excel have different spelling of functions, and in my version the function is

=binom.dist(r, n, p, cumulative)

If cumulative = 0, you get the value of exactly r successes in n trials.

If cumulative = 1, you get the value of at least r successes in n trials.

Thursday, October 4, 2018

Notes for Homework 7

Notes on t-scores

Notes on how to use the Population Pyramid website


Here are the cohort number for each gender and the total of the sexes from all the cohorts from 99 down. (The 100+ does not register at 0.1% for either males or females.) The cohorts in bold are the ones where the percentage is greater than the next youngest five year cohort.  If the birth rate about the same, you would expect that death rates would mean there would be less people in the 50-54 cohort than in the 45-49 group. In the United States, there was the big baby boom from 1945 through 1965. The last gasp of that increased birth rate is the reason the 50-54 cohort counts as a mode. We also had a smaller baby boom that ended in the past five years, the reason why the ages from 5-9 and 20-24 all count as modes. 

Cohort Male Female Total
95-99  0.0%  0.1%  0.1%
90-94  0.2%  0.4%  0.6%
85-89  0.5%  0.7%  1.2%
80-84  0.8%  1.1%  1.9%
75-79  1.2%  1.4%  2.6%
70-74  1.7%  2.0%  3.7%
65-69  2.4%  2.7%  5.1%
60-64  2.9%  3.1%  6.0%
55-59  3.4%  3.5%  6.9%
50-54  3.5%  3.5%  7.0%
45-49  3.2%  3.1%  6.3%
40-44  3.2%  3.2%  6.4%
35-39  3.1%  3.1%  6.2%
30-34  3.4%  3.5%  6.9%
25-29  3.5%  3.4%  6.9%
20-24  3.7%  3.5%  7.2%
15-19  3.3%  3.1%  6.4%
10-14  3.3%  3.1%  6.4%
05-09  3.3%  3.1%  6.4%
00-04  3.1%  3.0%  6.1%

Thursday, September 27, 2018