title: How do simple random sampling and dataframe SAMPLE function work in Apache Spark (Scala)?
body: <p>Q1. I am trying to get a simple random sample out of a Spark dataframe (13 rows) using the sample function with parameters withReplacement: false, fraction: 0.6 but it gives me samples of different sizes every time I run it, though it work fine when I set the third parameter (seed). Why so?</p>
  
  <p>Q2. How is the sample obtained after random number generation?</p>
  
  <p>Thanks in advance</p>