The table below shows the predictions by a classifier for a test dataset.

ID Target Prediction ID Target Prediction ID Target Prediction

$1$ false false $8$ true true $15$ false false

$2$ false false $9$ false false $16$ false false

$3$ false false $10$ false false $17$ true false

$4$ false false $11$ false false $18$ true true

$5$ true true $12$ true true $19$ true true

$6$ false false $13$ false false $20$ true true

$7$ true true $14$ true true

Calculate the error rate.