title: Calculating the probability that a value falls within a range in a normal distribution
body: <p>Example: what is the probability that an IQ score selected randomly falls between 80 and 110 inclusive?</p>
  
  <p>I have tried calculating this in two different ways and got different answers. Which one is correct?</p>
  
  <pre><code>sum(dnorm(80:110, 100, 15))
  # [1] 0.6722516
  pnorm(110, 100, 15) - pnorm(79, 100, 15)
  # [1] 0.6667508
  </code></pre>