Vern Cotter's side overwhelmed Japan and the United States in their opening two games before being given a reality check in a 34-16 defeat against South Africa and know they will have to be at their best to beat dangerous opponents with nothing to lose in Newcastle.
"We are playing this game as a qualifying game," Cotter said.
"We are enjoying being in the situation to qualify. We know it's going to be a very tough game. This probably rounds the whole thing up. We've got 80 minutes and we need to put in a very, very good performance."
Samoa may already be out of the reckoning for a place in the last eight, but Scotland will not be underestimating a side who beat the United States 25-16 before losing 46-6 to South Africa and 26-5 against Japan.
"We need to be careful not to fall into any traps," captain Greig Laidlaw said.
"We've got to give credibility and respect to Samoa. If we get our part right, we can cause Samoa problems."
Defeat would end Scotland's involvement in the tournament if Japan beat the United States in their last pool match. A high-scoring draw for Japan could also break Scottish hearts if Scotland lose without a bonus point.
"For a lot of us this is going to be the biggest match of our careers," Scotland No 8 David Denton said.
"For most of the people on our team this is our first World Cup, but now we've essentially got a playoff game."
Cotter will be relieved to have first-choice first five-eighth Finn Russell available after he missed the South Africa game. The New Zealand-born coach has also recalled hard-running centre Mark Bennett in a near full-strength team.
Samoa coach Stephen Betham, meanwhile, has made seven changes for the Pacific Islanders, fielding new combinations in midfield and among his loose forwards after losing to Japan in their previous game.
Rey Lee-Lo and George Pisi will form a new centre pairing, while Maurie Faasavalu, Jack Lam and Alafoti Faosiliva will be together in the back row for the first time.
Samoa: 1-Sakaria Taulafo, 2-Ma'atulimanu Leiataua, 3-Census Johnston, 4-Teofilo Paulo, 5-Kane Thompson, 6-Maurie Faasavalu, 7-Jack Lam, 8- Alafoti Faosiliva, 9-Kahn Fotuali'i (captain), 10-Tusi Pisi, 11-Fa'atoina Autagavaia, 12-Rey Lee-Lo, 13-George Pisi, 14-Paul Perez, 15-Tim Nanai-Williams
Replacements: 16-Motu Matu'u, 17-Viliamu Afatia, 18-Anthony Perenise, 19-Faifili Levave, 20-Vavae Tuilagi, 21-Vavao Afemai, 22-Patrick Faapale, 23-Ken Pisi
Scotland: 1-Alasdair Dickinson, 2-Ross Ford, 3-Willem Nel, 4-Richie Gray, 5-Jonny Gray, 6-Ryan Wilson, 7-John Hardie, 8-David Denton; 9-Greig Laidlaw (captain), 10-Finn Russell, 11-Tommy Seymour, 12-Matt Scott, 13-Mark Bennett, 14-Sean Maitland, 15-Stuart Hogg
Replacements: 16-Fraser Brown, 17-Gordon Reid, 18-Jon Welsh, 19-Tim Swinson, 20-Josh Strauss, 21-Henry Pyrgos, 22-Peter Horne, 23-Sean Lamont
