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What percentage of normally distributed scores lie under the normal curve?
100%. And that is true for any probability distribution.
What proportion of a normal distribution is located between the two z scores -1.25 and 1.25?
Approx 78.88 % Normal distribution tables give the area under the normal curve between the mean where z = 0 and the given number of standard deviations (z value) to its right; negative z values are to the left of the mean. Looking up z = 1.25 gives 0.3944 (using 4 figure tables). → area between -1.25 and 1.25 is 0.3944 + 0.3944 = 0.7888 → the proportion of the normal distribution between z = -1.25 and z = 1.25 is (approx) 78.88 %
Are these true of normal probability distribution IIt is symmetric about the mean TTotal area under the normal distribution curve is equal to 1 DDistribution is totally described by two quantities?
Yes, it is true; and the 2 quantities that describe a normal distribution are mean and standard deviation.
What does it mean normal distribution?
The Normal distribution is a probability distribution of the exponential family. It is a symmetric distribution which is defined by just two parameters: its mean and variance (or standard deviation. It is one of the most commonly occurring distributions for continuous variables. Also, under suitable conditions, other distributions can be approximated by the Normal. Unfortunately, these approximations are often used even if the required conditions are not met!
What is the area under standard normal distribution curve between z equals 0 and z equals -2.16?
2.16
What percentage of normally distributed scores lie under the normal curve?
100%. And that is true for any probability distribution.
Why does a researcher want to go from a normal distribution to a standard normal distributio?
A normal distribution simply enables you to convert your values, which are in some measurement unit, to normal deviates. Normal deviates (i.e. z-scores) allow you to use the table of normal values to compute probabilities under the normal curve.
What is the area under the normal curve between z scores of 1.82 and 2.09?
To find the area under the normal curve between z scores of 1.82 and 2.09, you can use the standard normal distribution table or a calculator. The area corresponding to a z score of 1.82 is approximately 0.9656, and for 2.09, it is about 0.9817. Subtracting these values gives the area between the two z scores: 0.9817 - 0.9656 = 0.0161. Thus, the area under the curve between z scores of 1.82 and 2.09 is approximately 0.0161, or 1.61%.
The total area under a normal distribution is infinite?
The total area under a normal distribution is not infinite. The total area under a normal distribution is a continuous value between any 2 given values. The function of a normal distribution is actually defined such that it must have a fixed value. For the "standard normal distribution" where μ=0 and σ=1, the area under the curve is equal to 1.
The distribution of sample means is not always a normal distribution Under what circumstances will the distribution of sample means not be normal?
The distribution of sample means will not be normal if the number of samples does not reach 30.
What is the area under the standard normal distribution called?
One.
Is total area under a normal distribution finite?
Yes, and is equal to 1. This is true for normal distribution using any mean and variance.
What is the area under the normal distribution curve between z 1.52 and z2.43?
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.
For a normal distribution find the z-scores values that separate the middle 60 percent of the distribution for the 40 percent in the tails?
The standard normal table tells us the area under a normal curve to the left of a number z. The tables usually give only the positive value since one can use symmetry to find the corresponding negative values. The middle 60 percent leaves 20 percent on either side. So we want the z scores that correspond to that 80 percentile which is .804. Therefore the values are are between z scores of -.804 and .804 * * * * * I make it -0.8416 to 0.8416
What is the total area under the normal distribution curve?
The area under the normal distribution curve represents the probability of an event occurring that is normally distributed. So, the area under the entire normal distribution curve must be 1 (equal to 100%). For example, if the mean (average) male height is 5'10" then there is a 50% chance that a randomly selected male will have a height that is below or exactly 5'10". This is because the area under the normal curve from the left hand side up to the mean consists of half of the entire area of the normal curve. This leads us to the definitions of z-scores and standard deviations to represent how far along the normal curve a particular value is. We can calculate the likelihood of the value by finding the area under the normal curve to that point, usually by using a z-score cdf (cumulative density function) utility of a calculator or statistics software.
How do you find the area of a normal distribution?
The area under a normal distribution is one since, by definition, the sum of any series of probabilities is one and, therefore, the integral (or area under the curve) of any probability distribution from negative infinity to infinity is one. However, if you take an interval of a normal distribution, its area can be anywhere between 0 and 1.
What percentage of scores falls between the mean and -2 to 2 standard deviations under the normal curve?
In a normal distribution, approximately 68% of scores fall within one standard deviation of the mean (between -1 and +1 standard deviations). About 95% of scores fall within two standard deviations (between -2 and +2 standard deviations). Therefore, the percentage of scores that falls specifically between the mean and -2 to 2 standard deviations is about 95% minus the 50% that is below the mean, resulting in approximately 45%.
