A z distribution allows you to standardize different scales for comparison.
You calculate the z-scores and then use published tables.
If the Z-Score corresponds to the standard deviation, then the distribution is "normal", or Gaussian.
For statistical tests based on (Student's) t-distribution you use the t-table. This is appropriate for small sample sizes - up to around 30. For larger samples (or degrees of freedom), the t-distribution becomes very close to the Standard Normal distribution so you use the z-tables.
To find the proportion of a normal distribution corresponding to z-scores greater than +1.04, you can use the standard normal distribution table or a calculator. The area to the left of z = 1.04 is approximately 0.8508. Therefore, the proportion of the distribution that corresponds to z-scores greater than +1.04 is 1 - 0.8508, which is approximately 0.1492, or 14.92%.
Tables of the cumulative probability distribution of the standard normal distribution (mean = 0, variance = 1) are readily available. Almost all textbooks on statistics will contain one and there are several sources on the net. For each value of z, the table gives Φ(z) = prob(Z < z). The tables usually gives value of z in steps of 0.01 for z ≥ 0. For a particular value of z, the height of the probability density function is approximately 100*[Φ(z+0.01) - Φ(z)]. As mentioned above, the tables give figures for z ≥ 0. For z < 0 you simply use the symmetry of the normal distribution.
If the distribution is Gaussian (or Normal) use z-scores. If it is Student's t, then use t-scores.
If the sample size is large (>30) or the population standard deviation is known, we use the z-distribution.If the sample sie is small and the population standard deviation is unknown, we use the t-distribution
You calculate the z-scores and then use published tables.
If the Z-Score corresponds to the standard deviation, then the distribution is "normal", or Gaussian.
For statistical tests based on (Student's) t-distribution you use the t-table. This is appropriate for small sample sizes - up to around 30. For larger samples (or degrees of freedom), the t-distribution becomes very close to the Standard Normal distribution so you use the z-tables.
It is the so-called "half-normal distribution." Specifically, let X be a standard normal variate with cumulative distribution function F(z). Then its cumulative distribution function G(z) is given by Prob(|X| < z) = Prob(-z < X < z) = Prob(X < z) - Prob(X < -z) = F(z) - F(-z). Its probability distribution function g(z), z >= 0, therefore equals g(z) = Derivative of (F(z) - F(-z)) = f(z) + f(-z) {by the Chain Rule} = 2f(z) because of the symmetry of f with respect to zero. In other words, the probability distribution function is zero for negative values (they cannot be absolute values of anything) and otherwise is exactly twice the distribution of the standard normal.
To find the proportion of a normal distribution corresponding to z-scores greater than +1.04, you can use the standard normal distribution table or a calculator. The area to the left of z = 1.04 is approximately 0.8508. Therefore, the proportion of the distribution that corresponds to z-scores greater than +1.04 is 1 - 0.8508, which is approximately 0.1492, or 14.92%.
In statistics, the "z" in a z-distribution refers to a standardized score known as a z-score. This score indicates how many standard deviations an individual data point is from the mean of a distribution. The z-distribution is a specific type of normal distribution with a mean of 0 and a standard deviation of 1, allowing for comparison of scores from different normal distributions.
11.51% of the distribution.
Tables of the cumulative probability distribution of the standard normal distribution (mean = 0, variance = 1) are readily available. Almost all textbooks on statistics will contain one and there are several sources on the net. For each value of z, the table gives Φ(z) = prob(Z < z). The tables usually gives value of z in steps of 0.01 for z ≥ 0. For a particular value of z, the height of the probability density function is approximately 100*[Φ(z+0.01) - Φ(z)]. As mentioned above, the tables give figures for z ≥ 0. For z < 0 you simply use the symmetry of the normal distribution.
To find the area under the normal distribution curve between z = 1.52 and z = 2.43, you can look up the z-scores in a standard normal distribution table or use a calculator. The area to the left of z = 1.52 is approximately 0.9357, and the area to the left of z = 2.43 is approximately 0.9925. Subtracting these values gives an area of approximately 0.9925 - 0.9357 = 0.0568. Thus, the area between z = 1.52 and z = 2.43 is about 0.0568.
z- statistics is applied under two conditions: 1. when the population standard deviation is known. 2. when the sample size is large. In the absence of the parameter sigma when we use its estimate s, the distribution of z remains no longer normal but changes to t distribution. this modification depends on the degrees of freedom available for the estimation of sigma or standard deviation. hope this will help u.... mona upreti.. :)