Thanks for the help.

- Thread starter bugle4one
- Start date

Thanks for the help.

I'm too lazy to write it in the fancy math symbols at the moment.

Regression Statistics

Multiple R 0.673777428

R Square 0.453976023

Adjusted R Square 0.449642499

Standard Error 218.4572976

Observations 128

ANOVA

df SS MS F Significance F

Regression 1 4999480.301 4999480.301 104.7590973 2.90218E-18

Residual 126 6013172.452 47723.59089

Total 127 11012652.75

Coefficients Standard Error t Stat P-value Lower 95% Upper 95%

Intercept -1200.199297 277.5496378 -4.324269009 3.08112E-05 -1749.461871 -650.9367233

X Variable 1 6.070724526 0.593122846 10.23518917 2.90218E-18 4.89695185 7.244497201

I then took known lengths from 50 fish and plugged them into the equation (y=6.0707x-1200.2; example of one estimate is 6.0707(673)-1200.2=2885 eggs) to produce 50 estimates of fish fecundity. Then I summed those up to estimate how many eggs went into the stream for a given year. Because I have 50 estimates, I'm a little confused how doing a bootstrap analysis off of the original data will provide me with a measure of variance around the summed point estimate. I must be confusing myself?

Thanks for your help

To get a bootstrap confidence interval, resample the original data (128 fish) with replacement and get an estimate of the slope and intercept for the resampled data. Use these new values of the slope and intercept with your 50 new fish to get the 50 egg estimates and add them up. This is bootstrap total number 1.

Repeat this a few thousand times and list all the bootstrap totals. Find the bottom and top 2.5%tiles. That is your 95% CI.

This way you are getting the whole range of possible slopes and intercepts and keeping the correlation between them.

If you don't have resampling software, write back and possibly I can help, or you can calculate the variance/covariance matrix from the data and someone else may give you a formula.

cheers, kat