[Why am i getting "formula parse error" when I try to classify the ages (column H) into groups using the following formula? And is there a better way? Thanks for your assistance:
=IF (H19<20, “0-19”, IF ((H19>=20 AND H19<40), “20-39”, IF ((H19>=40 AND H19<60), “40-59”, IF ((H19>=60 AND H19<70), “60-69”, IF (H19>=70, ">= 70", “WRONG”)))))
I was expecting to output the Age column into strings based on my category definitions.

What is the correct syntax to classify ages into groups using IF statements in Google Sheets?
The portions that you have formatted as (H19>=20 AND H19<40) should be changed to AND(H19>=20, H19<40). Your final formula should then be:
=IF(H19<20, “0-19”,
  IF(AND(H19>=20, H19<40), “20-39”,
  IF(AND(H19>=40, H19<60), “40-59”,
  IF(AND(H19>=60, H19<70), “60-69”,
  IF(H19>=70, ">= 70", “WRONG”)))))

Alternatively:
=IFS(OR(NOT(ISNUMBER(H19)),H19<0), "WRONG",
  H19<20, "0-19",
  AND(H19>=20, H19<40), "20-39",
  AND(H19>=40, H19<60), "40-59",
  AND(H19>=60, H19<70), "60-69",
  H19>=70, ">= 70")

