Hello. I have a tibble with 2 columns, each a nested list. I would like to make a new column where I look at each row and calculate the percentage of values in the cell of column_a that are greater than the values in the cell of column_b. The number of elements nested within each cell is the same, if that matters.

I know that there is a trick where if I can compare each value from the cell in col_a to the cell in col_b then I can take the mean of that vector to get the percentage I care about. I would like to use that way if possible but don't know how to do it when both are nested. Example: mean(vector_a > vector_b) gets the percentage I care about if I just had 2 vectors but I have a tibble full of them.

Example of a similar tbl with nested lists:

```
library(tidyverse)
n=10
a <- tibble(mu = c(3, 4, 5),
sd = 1) %>% mutate(column_a = map2(mu, sd, ~rnorm(n, .x, .y))) %>% select(column_a)
b <- tibble(mu = c(3, 4, 5),
sd = .8) %>% mutate(column_b = map2(mu, sd, ~rnorm(n, .x, .y))) %>% select(column_b)
combined <- bind_cols(a, b)
combined
```