A study shows that 70% of consumers believe cheaper supermarket brands are just as good as national name brands. In response to these findings, the manufacturer of a national brand asked a sample of shoppers whether they believe that supermarket chutney was as good as the national brand chutney.

A sample of 150 shoppers was tested and 90 believe that the supermarket brand is just as good as the national brand. Calculate the z-value. Round the answer to decimal places.