Stratified Samples ???

#1
Hi,

I'm having some trouble with this question.

The question asks

Stratified samples are widely used to study large areas of forest. Based on satellite images, a forest area in the Amazon basin is divided into 14 types. Foresters studied the four most commercially valuable types: alluvial climax, forests of quality levels 1, 2, and 3, and mature secondary forest. They divided the area of each type into large parcels, chose parcels of each type at random, and counted tree species in a 20- by 25-meter rectangle randomly placed within each parcel selected. Choose the stratified sample of 18 parcels. Be sure to explain how you assigned labels to parcels. If you use Table B, start at line 162.

Forest Type Total Parcels Sample Size
Climax 1 36 4
Climax 2 72 7
Climax 3 31 3
Secondary 42 4


Here is the table that I used

Line
162 97341 46254 88153 62336 21112 35574 99271 45297
163 64578 67197 28310 90341 37531 63890 52630 76315
164 11022 79124 49525 63078 17229 32165 01343 21394
165 81232 43939 23840 05995 84589 06788 76358 26622
166 36843 84798 51167 44728 20554 55538 27647 32708
167 84329 80081 69516 78934 14293 92478 16479 26974
168 27788 85789 41592 74472 96773 27090 24954 41474
169 99224 00850 43737 75202 44753 63236 14260 73686
170 38075 73239 52555 46342 13365 02182 30443 53229
171 87368 49451 55771 48343 51236 18522 73670 23212
172 40512 00681 44282 47178 08139 78693 34715 75606
173 81636 57578 54286 27216 58758 80358 84115 84568
174 26411 94292 06340 97762 37033 85968 94165 46514
175 80011

Here are my answers:

Forest Type Stratified Samples
Climax 1 34, 14, 15, 36, 23
Climax 2 34, 14, 62, 54, 15, 36, 23
Climax 3 14, 15, 23
Secondary 34, 14, 15, 36

Is this correct? If not how should I reevaluate this problem.

Thank You:)
 
#2
hey jena,

the only thing i notice is that you seem tohave started with line 162 for each strata, it may be better to start with line 162 for the first strata and then continue where you left off when going to the next strata.

it also appears that you have selected five samples from the Climax 1 catagory though your table above specifies 4, typo?

cheers
jerry
 
#3
Hi,

Actually I wasn't sure about if I could use the same number of stratified samples that I used for the sample type. Can I do that?

Thank You for your reply:)
 
E

elnaz

Guest
#4
Hello
for stratification samples there is a special formula for sampling in every stratum and its not necessary that sample size be the same in every stratum