[R-sig-Geo] Calculating median age for a group of US census blocks?

[Kevin Zembower]

Hello, all,

I'd like to obtain the median age for a population in a specific group 
of US Decennial census blocks. Here's an example of the problem:

## Example of calculating median age of population in census blocks.
library(tidyverse)
library(tidycensus)

counts <- get_decennial(
     geography = "block",
     state = "MD",
     county = "Baltimore city",
     table = "P1",
     year = 2020,
     sumfile = "dhc") %>%
     mutate(NAME = NULL) %>%
     filter(substr(GEOID, 6, 11) == "271101" &
            substr(GEOID, 12, 15) %in% c(3000, 3001, 3002)
            )

ages <- get_decennial(
     geography = "block",
     state = "MD",
     county = "Baltimore city",
     table = "P13",
     year = 2020,
     sumfile = "dhc") %>%
     mutate(NAME = NULL) %>%
     filter(substr(GEOID, 6, 11) == "271101" &
            substr(GEOID, 12, 15) %in% c(3000, 3001, 3002)
            )

I have two questions:

1. Is it mathematically valid to multiply the population of a block by 
the median age of that block (in other words, assign the median age to 
each member of a block), then calculate the median of those numbers for 
a group of blocks?

2. Is raw data on the ages of individuals available anywhere else in the 
census data? I can find tables such as P12, that breaks down the 
population by age ranges or bins, but can't find specific data of counts 
per age in years.

Thanks for your advice and help.

-Kevin