Z-distribution

Definition

The z-distribution, also known as the standard normal distribution, is a probability distribution that describes the set of standardized normal random variables. It is a fundamental concept in hypothesis testing and statistical inference, as it is used to determine the probability of obtaining a specific value or range of values from a normal distribution.

5 Must Know Facts For Your Next Test

1. The z-distribution is a standardized normal distribution with a mean of 0 and a standard deviation of 1.
2. The z-score, which is the number of standard deviations a data point is from the mean, is calculated by subtracting the mean and dividing by the standard deviation.
3. The z-distribution is used in hypothesis testing when the population standard deviation is known and the sample size is large (typically greater than 30).
4. The z-distribution is used to calculate the probability of obtaining a specific value or range of values from a normal distribution, which is essential for making statistical inferences.
5. The z-distribution is a key concept in the topic of Two Population Means with Known Standard Deviations, as it is used to determine the probability of the difference between two sample means being due to chance.

Review Questions

• Explain how the z-distribution is used in the context of hypothesis testing when the population standard deviation is known.
  • When the population standard deviation is known, the z-distribution is used in hypothesis testing to determine the probability of obtaining a specific sample statistic under the null hypothesis. The test statistic, which is typically the sample mean, is standardized by subtracting the hypothesized population mean and dividing by the known population standard deviation. This standardized value, known as the z-score, is then compared to the critical values of the z-distribution to determine the p-value and make a decision about the null hypothesis.
• Describe the role of the z-distribution in the topic of Two Population Means with Known Standard Deviations.
  • In the context of comparing two population means with known standard deviations, the z-distribution is used to determine the probability of the difference between the sample means being due to chance. The test statistic, which is the difference between the sample means, is standardized by dividing it by the square root of the sum of the variances of the two populations (divided by their respective sample sizes). This standardized value is then compared to the critical values of the z-distribution to calculate the p-value and make a decision about the null hypothesis, which typically states that the two population means are equal.
• Analyze how the properties of the z-distribution, such as the mean and standard deviation, influence the conclusions drawn in hypothesis testing and statistical inference.
  • The properties of the z-distribution, specifically the mean of 0 and the standard deviation of 1, are crucial in hypothesis testing and statistical inference. The standardization of normal random variables using the z-distribution allows for the comparison of sample statistics to a common scale, regardless of the original population parameters. This standardization enables the use of predetermined critical values and the calculation of p-values, which are essential for making decisions about hypotheses and drawing valid conclusions. The consistent mean and standard deviation of the z-distribution ensure that the conclusions drawn are based on a common, well-understood probability distribution, enhancing the reliability and interpretability of the statistical analysis.

Related terms

Standard Normal Distribution: The standard normal distribution is a normal distribution with a mean of 0 and a standard deviation of 1. It is the basis for the z-distribution and is used to standardize normal random variables.

Standardized Normal Random Variable: A standardized normal random variable is a normal random variable that has been transformed to have a mean of 0 and a standard deviation of 1. This transformation is done by subtracting the mean and dividing by the standard deviation.

Hypothesis Testing: Hypothesis testing is a statistical method used to determine whether a claim or hypothesis about a population parameter is supported by sample data. The z-distribution is used in hypothesis testing when the population standard deviation is known.