Normal distribution probability : Statistics S1 Edexcel June 2013 Q6(b) : ExamSolutions - youtube Video. Normal distribution is important in statistics and is often used in the natural and social sciences to represent real-valued random variables whose distributions are not known. There are also online sites available. The normal distribution density function f(z) is called the Bell Curve because it has the shape that resembles a bell.. Standard normal distribution table is used to find the area under the f(z) function in order to find the probability of a specified range of distribution. Since the normal distribution is symmetric about the mean, the area under each half of the distribution constitutes a probability of 0.5. Normal distribution is a continuous probability distribution. Find a) P(x < 40) b) P(x > 21) c) P(30 < x < 35) A radar unit is used to measure speeds of cars on a motorway. The most widely used continuous probability distribution in statistics is the normal probability distribution. The points so plotted can be compared with the straight line representing a normal distribution fitted to the data and so having the same mean and standard deviation. the total surface area (= probability) of a normal distribution is always exactly 1; the normal distribution is exactly symmetrical around its mean $$\mu$$ and therefore has zero skewness; due to its symmetry, the median is always equal to the mean for a normal distribution; the normal distribution always has a kurtosis of zero. Also an online normal distribution probability calculator may be useful to check your answers. There are many programs available that will calculate the probability for a normal curve including Excel and the TI-83/84. The normal probability distribution is a population distribution and all the distribution, i.e., discrete and continuous tends to the normal distribution when the sample size is large that is n>30. 3) View Solution. Normal Distribution. It is also called Gaussian distribution. Finding Probabilities from a Normal Distribution. Problems. The probability shown above is simply P (0 < X ≤ x )-- you can likewise manipulate the results as necessary to calculate an arbitrary range of values Part (a): Normal Distribution : S1 Edexcel January 2013 Q4(a) : ExamSolutions Statistics Revision - youtube Video . X is a normally normally distributed variable with mean μ = 30 and standard deviation σ = 4. Part (c): Finding Standard Deviation from a Normal Distribution : S1 Edexcel June 2013 Q6(c) : ExamSolutions - youtube Video. Since normal probability paper uses cumulative frequency or probability, data from a grouped frequency distribution should be plotted versus class boundaries, not class midpoints. The following examples show how to do the calculation on the TI-83/84 and with R. The command on the TI-83/84 is in the DISTR menu and is normalcdf(. Normal distribution or Gaussian distribution (according to Carl Friedrich Gauss) is one of the most important probability distributions of a continuous random variable.