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How do you to get the probability in normal distribution?
You calculate the z-scores and then use published tables.
How do you use the z-score to determine a normal curve?
If the Z-Score corresponds to the standard deviation, then the distribution is "normal", or Gaussian.
When do you use a z - table compared with when you use a t - table?
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.
How do you graph normal 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.
What is the normal distribution of 65 seconds and standard deviation 0.8?
If X is Normally distributed with mean 65 seconds and sd = 0.8 seconds, then Z = (X - 65)/0.8 has a Standard Normal distribution; that is, Z has a N(0, 1) distribution. The cumulative distribution for Z is easily available - on the net and in any basiic book on statistics. To get to the cumulative dirtribution function of X all you need is to use the transformation X = 0.8*Z + 65.
