Public opinion polls use sample sizes of more than 1000 people because it helps to ensure that the results are statistically significant. This means that the results are likely to be accurate and representative of the population as a whole.
The margin of error for a poll is the amount by which the results of the poll could be off from the actual results. The margin of error is calculated using the sample size, the confidence level, and the standard deviation of the population.
The confidence level is the probability that the results of the poll are within the margin of error. The standard deviation of the population is a measure of how spread out the opinions of the population are.
The larger the sample size, the smaller the margin of error will be. This is because the larger the sample size, the more likely it is that the sample will be representative of the population as a whole.
For example, if a poll has a sample size of 1000 people and a confidence level of 95%, the margin of error will be +/- 3%. This means that there is a 95% chance that the results of the poll are within 3% of the actual results.
If a poll has a sample size of 500 people and a confidence level of 95%, the margin of error will be +/- 4.4%. This means that there is a 95% chance that the results of the poll are within 4.4% of the actual results.
As you can see, the larger the sample size, the smaller the margin of error will be. This is why public opinion polls use sample sizes of more than 1000 people. It helps to ensure that the results are statistically significant and that they are likely to be accurate and representative of the population as a whole.