# ff_se_prod: Standard error for the product of two estimates In forsythfuture/FFtools: Consolidates common functions and commands used by Forsyth Futures

## Description

This function calculates the standard error for the product of two estimates. An example is if users want to derive the number of people working by multiplying the total population by the percentage of the population that is working.

## Usage

 `1` ```ff_se_prod(estimate_first, se_first, estimate_second, se_second) ```

## Arguments

 `estimate_first` Point estimate of the first value. `se_first` Standard error for the first estimate. `estimate_second` Point estimate of the second value. `se_second` Standard error for the second estimate

## Details

Reference for calculations: US Census Bureau, A Compass for Understanding and Using ACS Data, October 2008, A-16

## Value

The standard error of the derived products.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```df <- data.frame(pop = rnorm(n = 10, mean = 100000, sd = 20000), se_pop = rnorm(n = 10, mean = 1000, sd = 200), perc_working = runif(n = 10, min = .6, max = .9), perc_working_se = runif(n = 10, min = .05, max = .2)) # calculate standard errors of the products for each observation ff_se_ratio(df\$pop, df\$se_pop, df\$perc_working, df\$perc_working_se) # add columns to dataframe showing products and standard errors of products dplyr::mutate(df, total_working = pop / perc_working, se_total_working = ff_se_prod(pop, se_pop, perc_working, perc_working_se)) ```

forsythfuture/FFtools documentation built on Dec. 5, 2019, 3:16 a.m.