Hint: We need to know how to calculate the area under the curve for the given z value using the formula 
Here, A represents the area under the normal distribution curve and CL represents the confidence level. We then get the corresponding area. Using this area value, we look up the normal distribution table for the corresponding row and column and add the two to obtain the z value. Complete step-by-step solution:Let us consider the first case for which the given confidence level is 90 percent. In this case, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It can be calculated by using the formula 
Here, A represents the area under the normal distribution curve and CL represents the confidence level. Substituting the CL value as 0.90, we get
Adding and dividing by 2,
Looking for this value in the normal distribution table given below, we can see that this value lies close to the row containing 1.6 and column containing 0.05. It also lies close to the row containing 1.6 and column containing 0.04. So, we take a mean of these values to obtain the z value at this point.
Hence, the z value at the 90 percent confidence interval is 1.645.\n \n \n \n \n Let us consider the second case for which the given confidence level is 95 percent. In this case, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It is calculated by using the formula 
Substituting the values,
Adding and dividing by 2,
Looking for this value in the normal distribution table given above, we can see that this value lies on the row containing 1.9 and column containing 0.06. Adding the two values,
Hence, the z value at the 95 percent confidence interval is 1.96.Let us consider the third case for which the given confidence level is 99 percent. In this case too, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It is calculated by using the formula 
Substituting the values,
Adding and dividing by 2,
Looking for this value in the normal distribution table given above, we can see that this value lies on the row containing 2.5 and column containing 0.08. Adding the two values,
Hence, the z value at the 99 percent confidence interval is 2.58.Note: : It is important to take care while noting down the z value from the table, since it can be confusing and it is common to make errors while reading data from a table usually. It is important to know the concept of probability and statistics to solve this question. Answer from Vedantu Content Team on vedantu.com
Here, A represents the area under the normal distribution curve and CL represents the confidence level. We then get the corresponding area. Using this area value, we look up the normal distribution table for the corresponding row and column and add the two to obtain the z value. Complete step-by-step solution:Let us consider the first case for which the given confidence level is 90 percent. In this case, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It can be calculated by using the formula Here, A represents the area under the normal distribution curve and CL represents the confidence level. Substituting the CL value as 0.90, we get Adding and dividing by 2, Looking for this value in the normal distribution table given below, we can see that this value lies close to the row containing 1.6 and column containing 0.05. It also lies close to the row containing 1.6 and column containing 0.04. So, we take a mean of these values to obtain the z value at this point. Hence, the z value at the 90 percent confidence interval is 1.645.\n \n \n \n \n Let us consider the second case for which the given confidence level is 95 percent. In this case, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It is calculated by using the formula Substituting the values, Adding and dividing by 2, Looking for this value in the normal distribution table given above, we can see that this value lies on the row containing 1.9 and column containing 0.06. Adding the two values, Hence, the z value at the 95 percent confidence interval is 1.96.Let us consider the third case for which the given confidence level is 99 percent. In this case too, we need to calculate the area under the curve and it can be given as shown in the figure below. \n \n \n \n \n It is calculated by using the formula Substituting the values, Adding and dividing by 2, Looking for this value in the normal distribution table given above, we can see that this value lies on the row containing 2.5 and column containing 0.08. Adding the two values, Hence, the z value at the 99 percent confidence interval is 2.58.Note: : It is important to take care while noting down the z value from the table, since it can be confusing and it is common to make errors while reading data from a table usually. It is important to know the concept of probability and statistics to solve this question. Answer from Vedantu Content Team on vedantu.comZ Score Table
z-table.com › 99-confidence-interval-z-score.html
99 Confidence Interval Z Score - Z SCORE TABLE
Find out how to calculate and use our confidence interval calculator to determine the 99% confidence interval z-score. Learn its significance and application.
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How to calculate confidence interval?
To calculate a confidence interval (two-sided), you need to follow these steps:
- Let's say the sample size is
100. - Find the mean value of your sample. Assume it's
3. - Determine the standard deviation of the sample. Let's say it's
0.5. - Choose the confidence level. The most common confidence level is
95%. - In the statistical table find the Z(0.95)-score, i.e., the 97.5th quantile of N(0,1) – in our case, it's
1.959. - Compute the standard error as
σ/√n = 0.5/√100 = 0.05. - Multiply this value by the z-score to obtain the margin of error:
0.05 × 1.959 = 0.098. - Add and subtract the margin of error from the mean value to obtain the confidence interval. In our case, the confidence interval is between 2.902 and 3.098.
omnicalculator.com
omnicalculator.com › statistics › confidence-interval
Confidence Interval Calculator
What is the z-score for 99% confidence interval?
The z-score for a two-sided 99% confidence interval is 2.807, which is the 99.5-th quantile of the standard normal distribution N(0,1).
omnicalculator.com
omnicalculator.com › statistics › confidence-interval
Confidence Interval Calculator
What is the Z-score for a 99% confidence interval?
The z-score for a two-sided 99% confidence interval is 2.807, which is the 99.5-th quantile of the standard normal distribution N(0,1).
omnicalculator.com
omnicalculator.com › statistics › 99-confidence-interval
99% Confidence Interval Calculator
Statistics LibreTexts
stats.libretexts.org › bookshelves › introductory statistics › statistics with technology 2e (kozak) › 12: appendix- critical value tables
12.2: Normal Critical Values for Confidence Levels - Statistics LibreTexts
January 6, 2022 - Critical values for \(Z_{c}\) created using Microsoft Excel
Omni Calculator
omnicalculator.com › statistics › 99-confidence-interval
99% Confidence Interval Calculator
June 11, 2024 - The z-score for a two-sided 99% confidence interval is 2.807, which is the 99.5-th quantile of the standard normal distribution N(0,1).
MathBlog
mathblog.com › statistics › definitions › z-score › ci › 99-to-z
99% Confidence Interval to Z-score
April 22, 2024 - Find the Z-score in the Z-table: Look up the area closest to 0.995 in the Z-table. The Z-score that corresponds to this area is approximately 2.58. This is the value that indicates our data point is 2.58 standard deviations from the mean.
Study.com
study.com › skill › learn › how-to-find-the-critical-z-value-for-a-given-confidence-level-explanation.html
How to Find the Critical Z-value for a Given Confidence Level | Statistics and Probability | Study.com
Step 3: Use the {eq}z {/eq}-table (or a calculator) to obtain the {eq}z {/eq}-score {eq}z_{\alpha/2} {/eq}. The terms and symbols defined below are applied when using the steps to find the critical Z-value for a given confidence interval.
Statology
statology.org › home › how to find z alpha/2 (za/2)
How to Find Z Alpha/2 (za/2)
November 4, 2020 - For example, for some test that ... critical values for different values of α: ... For a test using a 90% confidence level (e.g. α = 0.1), the z critical value is 1.645....
Sage Calculator
sagecalculator.com › critical-z-values-calculator
Critical Z Values Calculator - Sage Calculator
July 3, 2025 - 5. How do I use Z value in confidence intervals? CI = x̄ ± Z * (σ/√n) 6. What Z value do I use for a 99% confidence level?
CK-12 Foundation
flexbooks.ck12.org › cbook › ck-12-interactive-algebra-2-for-ccss › section › 6.4 › primary › lesson › critical-values-alg-2-ccss
Critical Values
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Omni Calculator
omnicalculator.com › statistics › confidence-interval
Confidence Interval Calculator
December 13, 2016 - Then you can calculate the standard error and then the margin of error according to the following formulas: ... where Z(0.95) is the z-score corresponding to the confidence level of 95%. If you are using a different confidence level, you need ...
Fiveable
library.fiveable.me › all key terms › ap statistics › critical value (z-score)
Critical Value (z-score) - (AP Statistics) - Vocab, Definition, Explanations | Fiveable | Fiveable
Next, consult a standard normal distribution table or use statistical software to find the z-score corresponding to an area of 0.995 (1 - 0.005). The critical value at this point is approximately 2.576, which will then be used in your confidence interval calculation...
Crafton Hills College
craftonhills.edu › current-students › tutoring-center › mathematics-tutoring › distribution_tables_normal_studentt_chisquared.pdf pdf
Confidence Interval Critical Values, zα/2 Level of Confidence
Confidence Interval Critical Values, zα/2 · Level of Confidence · Critical Value, z α/2 · 0.90 or 90% 1.645 · 0.95 or 95% 1.96 · 0.98 or 98% 2.33 · 0.99 or 99% 2.575 · Hypothesis Testing Critical Values · Level of Significance, α · Left-Tailed · Right-Tailed ·
Coconino Community College
coconino.edu › resources › files › pdfs › academics › sabbatical-reports › kate-kozak › appendix_table.pdf pdf
Appendix: Critical Values Tables 433 Appendix: Critical Value Tables
Table A.2: Critical Values for t-Interval · Appendix: Critical Values Tables · 434 · Table A.1: Normal Critical Values for Confidence Levels · Confidence Level, C · Critical Value, zc · 99% 2.575 · 98% 2.33 · 95% 1.96 · 90% 1.645 · 80% 1.28 · Critical Values for Zc created using ...
Alchemer
alchemer.com › home › blog › how to calculate confidence intervals
Mastering the Calculation of Confidence Intervals
December 5, 2024 - Since they have decided to use a 95 percent confidence interval, the researchers determine that Z = 1.960. Next, the researchers would need to plug their known values into the formula.
Southeastern
www2.southeastern.edu › Academics › Faculty › dgurney › Math241 › StatTopics › ZAlpha.htm
Finding Z Alpha over 2
You should see “invNorm(” on your calculator screen. Type in 0.005, add a right parenthesis and press the “ENTER” key. The result, rounded to three decimal places, is the opposite of Zα/2. Consequently, Zα/2 = 2.576 for 99% confidence.
Reddit
reddit.com › r/athabascauniversity › mgsc 301 - z-score for 99% confidence level (chapter 8)
r/AthabascaUniversity on Reddit: MGSC 301 - Z-score for 99% confidence level (Chapter 8)
May 7, 2023 -
Hi everyone, I’m trying to figure out if the z-score for 99% confidence level should be 2.578 or 2.576 (as noted in the textbook). Every time I use the cumulative probability table to map it, I end up with 2.578.
Stats4stem
stats4stem.org › introduction-to-confidence-intervals
Introduction to Confidence Intervals
nd the z* value for a 99% confidence level is 2.58. ... The standard error is the standard deviation OF THE STATISTIC. Make sure to do this calculation and NOT just use the standard deviation given! For example, let's say you are constructing a 1 sample mean confidence interval and you know ...
Simon Fraser University
sfu.ca › personal › archives › richards › Zen › Pages › Chap17.htm
Chapter 17. z-test for differences between means
The 99% confidence interval will thus be 39.6250 ± 2.58 × 1.5798 or 39.6250 ± 4.0759 or 35.5491 to 43.7009. 12. Can you conclude that the readers of Q&V are older than the readers of W-Xers? Determine whether the difference between the sample means is statistically significant.