A researcher wants to know the average age of teachers in a certain community. 50 teachers from junior high school and 25 teachers from senior high school were interviewed for the purpose. How will the researcher choose a sample size of 20 using:1. Simple Random Sampling -2. Systematic Random sampling -3. Stratified Random Sampling -4. Cluster Sampling -

Class iii atmospheric hazards are those involving

Which of the following must happen in order for productivity to increase? a. production levels remain unchanged while inputs increase. b. production levels rise while inputs decrease. c. production levels fall while inputs increase.

In an ecosystem, marsh snails feed on phytoplankton and painted turtles feed on marsh snails. pollution has resulted in the depletion of phytoplankton. what effect would this situation likely have on the population of marsh snails and painted turtles? as phytoplankton were destroyed, the population of marsh snails would most likely then the population of painted turtles would mostly likely a. 1. increase 2. decrease 3. stay the same b. 1. increase 2. decrease 3. stay the same