Finding z critical values for Confidence Interval


  • Since we use the left cumulative z-table, we need to find the left-tailed area to find the negative z-critical value.
  • First, subtract the given confidence level from one and then divide it by 2 to get the left area.
  • Look up the table using the left area to find one of the critical values.
  • Once we get the negative critical value, then make it positive to have another one.
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