Question

which method of gathering data will be most effective in learning how diet and fitness choices affect long - term health?
an experiment
an observational study
a sample survey
a census

Explanation:

To determine the most effective method for learning how diet and fitness choices affect long - term health, we analyze each option:

• An experiment: In an experiment, we can control variables (like diet and fitness regimens) and randomly assign participants to different groups (e.g., a group with a specific diet and exercise plan, and a control group with a different or no - intervention plan). This allows us to establish cause - and - effect relationships between diet, fitness, and long - term health outcomes.
• An observational study: In an observational study, we just observe and record the behaviors and health outcomes of people without intervening. But since we don't control the diet and fitness variables, it's hard to determine if a particular diet or fitness choice is the cause of a health outcome (there could be confounding variables).
• A sample survey: A sample survey is mainly used to collect people's opinions, self - reported behaviors, or statuses. It can't establish cause - and - effect relationships between diet, fitness, and health as effectively as an experiment, as it relies on self - reports which may be inaccurate and doesn't involve manipulating variables.
• A census: A census aims to collect data from an entire population. It's not designed to study cause - and - effect relationships between diet, fitness, and health; it's more about getting a comprehensive count and description of a population.

So, an experiment is the most effective method as it can help establish the causal link between diet, fitness choices, and long - term health.

Answer:

an experiment