A standard normal distribution is a normal distribution with mean 0 and standard deviation 1.
The standard normal distribution is a special case of the normal distribution. It is the distribution that occurs when a normal random variable has a mean of zero and a standard deviation of one. The normal random variable of a standard normal distribution is called a standard score or a z-score. Every normal random variable X can be transformed into a z score via the following equation: z = (X - μ) / σ. where X is a normal random variable, μ is the mean of X, and σ is the standard deviation of X A standard normal distribution is a normal distribution with zero mean () and unit variance (), given by the probability density function and distribution function. (1). (2). over the domain.  A standard normal distribution table shows a cumulative probability associated with a particular z-score. Table rows show the whole number and tenths place of the z-score. Table columns show the hundredths place. The cumulative probability (often from minus infinity to the z-score) appears in the cell of the table. It is the distribution that occurs when a normal random variable has a mean of zero and a standard deviation of one. The normal random variable of a standard normal distribution is called a standard score or a z-score. The Standard Normal Distribution. A standard normal distribution is a normal distribution with mean 0 and standard deviation 1. Areas under this curve can be found using a standard normal table (Table A in the Moore and Moore & McCabe textbooks). All introductory statistics texts include this table. Some do format it differently.  A normal distribution with a mean of 0 and a standard deviation of 1 is called a standard normal distribution. Areas of the normal distribution are often represented by tables of the standard normal distribution. Area below 26 in a normal distribution with a mean of 50 and a standard deviation of 10. If all the values in a distribution are transformed to Z scores, then the distribution will have a mean of 0 and a standard deviation of 1. For the standard normal distribution, 68% of the observations lie within 1 standard deviation of the mean; 95% lie within two standard deviation of the mean; and 99.9% lie within 3 standard deviations of the mean. To this point, we have been using X to denote the variable of interest (e.g., X=BMI, X=height, X=weight). In this case, because the mean is zero and the standard deviation is 1, the Z value is the number of standard deviation units away from the mean, and the area is the probability of observing a value less than that particular Z value. Note also that the table shows probabilities to two decimal places of Z. The Standard Normal Distribution. The standard normal distribution is a normal distribution with a mean of zero and standard deviation of 1. The standard normal distribution is centered at zero and the degree to which a given measurement deviates from the mean is given by the standard deviation. In this case, because the mean is zero and the standard deviation is 1, the Z value is the number of standard deviation units away from the mean, and the area is the probability of observing a value less than that particular Z value. Note also that the table shows probabilities to two decimal places of Z. If and, the distribution is called the standard normal distribution or the unit normal distribution denoted by and a random variable with that distribution is a standard normal deviate. For the normal distribution, the values less than one standard deviation away from the mean account for 68.27% of the set; while two standard deviations from the mean account for 95.45%; and three standard deviations account for 99.73%.
http://stattrek.com/probability-distributions/standard-normal.aspx http://mathworld.wolfram.com/StandardNormalDistribution.html http://stattrek.com/probability-distributions/standard-normal.aspx http://www.oswego.edu/~srp/stats/z.htm http://onlinestatbook.com/2/normal_distribution/standard_normal.html http://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/BS704_Probability/BS704_Probability9.html http://sphweb.bumc.bu.edu/otlt/MPH-Modules/BS/BS704_Probability/BS704_Probability9.html https://en.wikipedia.org/wiki/Normal_distribution
in a standard normal distribution the mean is