This survey is part of an on-going poll conducted from the time Najib took office as PM, and closed by the time AH1N1 arrived.
During the whole survey period, Dato' Seri Najib's approval rate has never breach or even touches the 50% barrier. His worst approval ratings had been 34%, in July 2008, and the March 3-9 period in 2009. But, through statistic, his approval rating has since then increase. This is more or less the effects of his on-going image rebulding mission.
The poll was carried out between 6th-15th May & the poll has a margin of error estimated plus minus 3.10%. You can have a look of the findings here.