how to fine this. The confidence level is 99%, so the Z-score is approximately 2.576 (you can find this value in a standard Z-table or using a calculator)

It seems like you're asking how to find the Z-score for a 99% confidence level. Here are the steps:

1. Identify the confidence level: In this case, the confidence level is 99%.

2. Convert the confidence level to a two-tailed test: Since we're dealing with a two-tailed test (meaning we're considering both ends of the distribution), we need to adjust the confidence level. The two-tailed confidence level is 100% - (100% - 99%)/2 = 99.5%.

3. Look up the Z-score in a standard Z-table: A Z-table, also known as a standard normal table or unit normal table, is a mathematical table that shows the cumulative probabilities for a standard normal distribution. For a confidence level of 99.5%, the Z-score is approximately 2.576.

4. If you don't have a Z-table, you can use a calculator: Many scientific calculators have a function that allows you to calculate the Z-score. You would input the confidence level (in this case, 0.995 for 99.5%) and the calculator would give you the Z-score.

So, the Z-score for a 99% confidence level is approximately 2.576.